Same problem here. Things is this problem happen occasionally, and when I click save the workflow with a Telegram trigger turn on, the error message appear and prevent me to save or sometimes (when the workflow is inactive) prevent me to active the workflow. But if i just do nothing and wait for 10 minutes then i can save and active workflow like normal.
After a bit of research I think this problem related to your domain SSL certificate. But I don’t know the solution for it.
I’m self hosting my n8n too with a domain i bought (very cheap) and looking hard to a way to solve this too. Very annoying.