A checklist:
It could be that you're not logged in with your private key, you're offline or not connected to the relays. A quick way to see whether you're logged in with your private key (nsec) is to see whether the DMs are open and whether you can read their content.
https://github.com/irislib/faq
I can see DMs
Just can't send or reply
Please Login to reply.
Could also be that your relays are not allowing you to write to them new events (read-only access) .
Is there a way to "fix" that?
Find free relays or pay for the restricted ones.