This sort of thing is always hard to work out because it’s somewhere in the space between two different systems! But I’d suggest that, on cycle.travel, you go to ‘My bike’ then ‘Profile’.

You’ll see a section about ‘Login details’ which has details about your connected accounts. Click ‘Remove Garmin Connect link’. This will drop the link between cycle.travel and your Garmin Connect account.

Then go through the Garmin Connect setup again – i.e. try to send one of your cycle.travel routes to Garmin Connect, and it should prompt you to make the connection again. Hopefully that will fix it.