Yep, regarding Salesforce integration - everything is working as usual on our side. Are you using a custom OAuth client? Maybe clientid/secret got mixed up from different environments etc
Thanks for your help. It all started when I was configuring a connector for a new sandbox I cloned from the production one. Since I kept getting that error, I checked the staging connector, which, coincidentally, had an authorization token that expired yesterday. So I tried again in my staging sandbox and got the same error. I suspect there might be browser-side issues, because I haven't configured custom OAuth for EasyMorph in my organizations. If I can figure it out, I'll let you know. I'll also try contacting their support team.
Ok I found a solution! Setup>Apps>Connected Apps> Easymorph Dev Connected App
I clicked “install” here and tried the Authorization flow again. It failed once but with a new error message. Unfortunatly I was too exited to make a screenshot.. I tried again and now I’m successfully authorized in a partial copy sandbox.