How to debug connectivity issues with ActivityPub

I see a lot of error 403. That’s why my first though was it is either bot list or geo blocking. But I can’t find anything from user agents when browsing error.log and I mostly try from instances located in Finland or other than some very problematic countries. Australia was a headache at some point (do we really need geo blocking here is worth of other topic, but because of my history with WordPress I’m using it).

Something like this:

[Discourse Activity Pub] GET request received by https://foorumi.katiska.eu/ap/actor/701e86455ed584115e0d22ddf294698c failed: 403 Forbidden

I understand something like this would happen if there is an instance that I’ve not allowed, but it happens with everyone

I can connect my Discourse user to a Mastodon user, though.

Using Discourse plugin. Nothing fancy. I’m not using Cloudflare because there is no point on small forum located in Finland and serving finnish users.