TDX SP; the screen reported 'the following is missing' and showed a picture of the chair. It said to reset, which then brought up a message saying 'ctl not connected'.

Hi,
Seems the Control Panel is not connected properly on the unit or may have gone lose check the control panel cable connection on the unit.
Make sure that when check the connection it is turned OFF and not plugged in or charging to avoid any short or shock.
See below for info on how to check the control panel connection,


See picture below to check the controller connection form the battery.
If the issues till exist then probably the controller program is corrupted or may need reprogramming on the unit.
The reprogramming can only be done by a service technician of Invacare for the reprogramming of the controller if you still have the Manual supplied with the wheel chair it should have the info ther and number to call, if ever the connection is not the issue.
I hope this helps.
Have a nice day,
mvincentc