Home Assistant relies on websockets, which basically are a “stay open” type of connection, and requires extra configuration on the reverse proxy side to allow websockets to work. Which proxy are you trying to use?
To rule out the block issue on the Home Assistant side, you can TEMPORARILY add this to your config:
This will completely open the Home Assistant block and allow any reverse proxy to go through. If this works then the issues is not specifying the right IP for the trusted proxy. If it still doesn’t work even after allowing all IPs, the issue is on your reverse proxy configs and likely not on the Home Assistant side (likely not configuring websockets properly). I say Temporarily set this only for testing because leaving it like this overrides the security and leaves your system vulnerable to attacks, which is the reason specifying this IP was added as a requirement last year.
Took another look at your post and possibly its just a YAML formatting issue. Move the IP to another line and indent it with a dash instead of putting it right after the colon. Try this instead of what you have: