Hello, I have att uverse I never had a problem logging into Target's ehr until I got a new laptop, now I get the same error you are getting. I don't think that it is the service provider, I think it has something to do with Target's site. I can logon at work, and at my dad's house with his computer but not mine (he has uverse to).
They had alot of problems with handling server requests in the past due to dated server architecture but since they upgraded their server limits source: Target eHR or https://weserveyou.me/target-ehr-team-member-services/ the performance has increased quite a significant bit. I normally dont have any problems with it now but if you seem to have any shoot me a email.