I can’t see any content from https://lemmy.ca/c/progressivepolitics@lemmy.world even though the community is right there https://lemmy.world/c/progressivepolitics
Instead I see a “Error! There was an error on the server” message.
As far as I can tell from my modlog and the modlog of the community I haven’t been banned.
I can see other lemmy.world communities, like for example https://lemmy.ca/c/world@lemmy.world so I don’t think some kind of block at the instance level has happened.
What is going on?

It could be blocked/defederated by lemmy.ca
As far as I understand it, blocks and defederations happen at the instance level, but like I said I can access other lemmy.world communities.