Passenger seat belt does not buckle.

either failing seat switch or female buckle ---check wiring to both

Heating and the cooling both don't work ? Just one seat or all seats ?
Your best bet have it checked for DTC'S - diagnostic trouble codes to start .
Climate Controlled Seat Module (CCSM) Diagnostic Trouble Code (DTC) Index DTC Description Source Action B1342 ECU Is Faulted CCSM INSTALL a new CCSM and CARRY OUT programmable module installation (PMI). REFER to Climate Controlled Seat Module . B1358 Ignition Switch or Blower Electronics Circuit Short to Ground CCSM Go To Pinpoint Test Q . B2477 Module Configuration Error CCSM This DTC indicates programmable module installation (PMI) has not been done to a newly installed module. CARRY OUT PMI. REFER to Section 418-01 . CLEAR the DTC. CARRY OUT the self-test. B2486 Climate Controlled Seat Module Voltage Out of Range CCSM DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 294 (WH/LB) for a fault. REPAIR as needed. If okay, REFER to Section 414-01 . Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . B2488 Thumbwheel Switch Voltage Out of Range High CCSM Go To Pinpoint Test R . B2521 Tach Circuit Failure CCSM Go To Pinpoint Test Q . B2729 Cushion Over-Temp Detected CCSM Go To Pinpoint Test S . B2730 Back Over-Temp Detected CCSM Go To Pinpoint Test S . B2731 Differential Temperature Fault CCSM Go To Pinpoint Test S . B2792 Heat Switch Short to Ground CCSM NOTE: If HEAT is pressed for greater than 20 seconds on the climate controlled seat switch, DTC B2792 will set in the CCSM.
CLEAR the DTC. If the DTC does not clear, DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 1551 (VT/WH) for a short to ground. REPAIR as needed. If okay, INSTALL a new climate controlled seat switch. Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . B2793 Cool Switch Short to Ground CCSM NOTE: If COOL is pressed for greater than 20 seconds on the climate controlled seat switch, DTC B2793 will set in the CCSM.
CLEAR the DTC. If the DTC does not clear, DEPOWER the supplemental restraint system (SRS). REFER to Section 501-20B . DISCONNECT driver safety belt buckle pretensioner electrical connector or passenger safety belt buckle pretensioner electrical connector of the affected seat and CONNECT restraint system diagnostic tool 418-F395 to the safety belt buckle pretensioner harness connector. CONNECT the battery ground cable. CHECK circuit 1550 (WH/OG) for a short to ground. REPAIR as needed. If okay, INSTALL a new climate controlled seat switch. Once the repair is complete, DISCONNECT the restraint system diagnostic tool from the safety belt buckle pretensioner harness connector and CONNECT the safety belt buckle pretensioner connector of the affected seat. REPOWER the SRS. REFER to Section 501-20B . U2362 UBP Invalid Data Node ID CCSM NOTE: DTC U2362 indicates a network concern, the CCSM is not the source of the fault.
CLEAR the DTC. If the DTC does not clear, REFER Section 418-01 .

Sorry. I was exhausted and frustrated when I wrote the original post. Hopefully this clarifies:

The latching mechanism does not retract all the way when the button is pushed which does not allow the seat belt to be inserted all the way.

I fiddled with the passenger seat belt and found that that was the issue. I just need to know if I can fix that myself or if it needs to be replaced.

Its a 2015, take it back to the dealer. Sounds like a bad sensor.

Two Female Torx (E-30 i think) located front and rear of the seat slider (move the seat all the way back and then all the forward to expose them. WARNING ***DO NOT HAVE THE IGNITION ON WHEN DISCONNECTING THE ELECTRIC FROM THE SEAT AND SEAT BELT BUCKLE. It would cause the Airbag to be set off.

The switch may be bad inside the female end of the seat belt buckle.

When you buckle both ends of the belt together, the switch is opened and no longer allows current to reach the dash light.

The switch is probably bad or your buckle ends are not completely connecting.

If the latter is the case, that places the wearer in jepordy in case of a crash.

Can they be poked down and then brought up where you say? I had this on a lincoln town car and they were long enough without an extension. The mounting bolts are really made in only one spot usually and are very importantly secured. You could always just buy a female strap without any plastic on it and run it whever you want. A lot of RV places carry them :>) Hope this helps.

You can normally unplug the sensor that is on the floor under the seat, either attached or close to seatbelt.

try a local wrecking yard most all years fit up to 2000

I need to replace the rear passenger-side seat belt buckle clasp but the clasp (under back seat) is connected to the seatbelt for middle backseat passenger.Can I replace just the passenger side without disturbing the middle belt?, cheers,Jen.