I found various resources online and methods of re-pairing. I would share the method I used to successfully re-pair the remote.
Remove fuse 1 (80amp) and Fuse 22 (25 amp) located under the driver's seat at the front. I found the easiest access was when the seat was partially spun round.
Once the fuses are out wait at least 5 seconds and then re-insert together ( a little tricky) and within 5 seconds press the off button on the transmitter for at least 1 second.
You should then get a solid green or red light when you press the buttons indicating the remote is now paired.
I have included a pic of the fuse layout and the instructions from the Webasto telestart instructions
I hope you find this useful and from what I can see on line it will also work for newer versions.