R1200RT won't start nothing at all, battery is charged . Bike was left standing for over a month.

the new battery may need charging
put it on a charger or go for a good long ride to charge it up
is the battery terminals tight

This bike has fuel injection and will not start if the battery is flat or has a low charge bumping it will not work
if you have had cold weather over the last five months I would expect that the battery is dead and will need replacing
when you have replaced the battery it should be fine

What I would suggest then is to bridge the side stand switch. If the switch stays open circuit, it will never start but if you bridge the wires before the switch then the bike should start and have now solved the problem for the interim or you if it does not start you know you have to look elsewhere.

Please get back if you require anything else or give favorable feedback.

Thank you

Check the clutch, neutral and side stand safety interlocks.
Double check that the bike is in neutral, and the clutch is pulled in when trying to start the bike.
If the bike is in gear with the side stand down, the bike cuts off all ignition.
If the clutch isn't pulled in, the starter won't engage.
Check all these safety interlock switches, and make sure you are in neutral with the clutch in when trying to start the bike.

Sounds like the battery may not be charged. Put a charger on the battery, bring to a full charge. Try starting. If it won't crank, locate a load tester and check the battery for weakness/dead cell. If the battery is not the problem, the starter/starter solenoid may have corroded/dirty contacts.

if the starter wont turn the engine over try putting the bike on its center stand plonking it in top gear and turning the rear wheel to see if the engine is sezed up,, it may just be very tight,,,or the starter may have set solid from lack of use, also the battery is by now dead,,,18 months stood doing nothing and not chareds very often wont do it any good at all, try using a car battery to jump start the bike

if the alternator on your k100 is ok, then its the battery not getting charged or its a dud one, if a battery is left sitting about for a long time it's battery plates sulphate, after this happens it wont take a charge ever again so dump it and put a new one on it, i have a k75rtic grate bikes but they do go wrong at times, batterys are not cheep, so keep it fully charged up over the winter with a solar charger or if left for a long time to stand,
ps,, dont run the bike up unless you run it till its fully warmed up, or the choke floods the motor up the next time you try to start it up it only turns off when its warm, and has nothing to do with the leaver on the handel bar's,, this only raises the reves!