Ah, okay, but that was in v4 that you turned off DNS and used your ISPs one, because in v5 this option is no longer possible. Check this topic:
So it seems that your ISP tries to enforce it’s own DNS (sometimes) and then doesn’t allow other connections. This actually should be no problem if you enable a DoH server… but it seems to be.
Could you try to disable Blokada and set the private DNS to for example Cloudflare and check whether that works:)?
All those DNS had a [DoH] behind the name?