Repeatedly asking for Server Credentials and failing to add data for online layers.

[OllyD]

Hi,

Yesterday a number of feature layers hosted on ArcGIS online stopped being able to be loaded into ArcPRO.

Whenever I open a APRX that references these layers I get the red "!" and if I try to repair the data source nothing happens. 

If I try to add the data manually it ask me for my server credentials, if I put them in and select OK the window just reappears. If I press cancel I get the  "Failed to add data" error.  

In addition I can load these data sets fine into ArcMap but not Pro. 

Does anyone have any ideas that might cause this sort of error?

Thanks

[OllyD]

Some further context, these layers work fine for other members of the team but not me, despite myself being the owner of the layers.