I found the problem. It has to do with network security provider injecting JS into my browser to support their safety features such as SafePay, SafeBrowsing, etc..
Once I turned of the JS injection it worked fine. The only weird thing is that I have the injection setting turned on for another computer and everything is working fine.
Does the HubSpot UI present an error as well? Could you share that in this thread and send me the auth URL (oauth/authorize?client_id=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx&scope=contacts%20automation&redirect_uri=https://www.example.com/) you are using via direct message?
I found the problem. It has to do with network security provider injecting JS into my browser to support their safety features such as SafePay, SafeBrowsing, etc..
Once I turned of the JS injection it worked fine. The only weird thing is that I have the injection setting turned on for another computer and everything is working fine.