My Trackmania freezes while connecting and goes into "not responding"

[grave zenith]

do you have both diegetic information display and split speeds installed as openplanet plugins?

and did you happen to update diegetic information display earlier today?

[shrewd citrus]

If this is the case, then manually updating Split Speeds can fix it: https://openplanet.dev/plugin/splitspeeds (download the .op file, place it in C:/Users/Username/OpenplanetNext/Plugins/)