Dear @adventurediscoverer,
Arcgis is beyond my skills, read https://help.mapillary.com/hc/en-us/articles/115003949249-Mapillary-for-ArcGIS-Pro : first, that page is dated ‘4 years ago - updated’ ; then, in the summer of 2021 Mapillary upgraded the API from v.3 to v.4 ; from the forum learned this broke queries, login credentials / keys , plus for example picture references were ‘converted’ to a new template , which in turn broke mapillary references in Open Street Map : it might (or not, that’s beyond my ken) turn out that the Arcgis plugins haven’t been ‘converted’ yet - given that I don’t recall posts on the Arcgis plugin being updated (searched, spot : Is the ArcGIS Web Appbuilder widget no longer supported? [Solved] ) ; that the most recent comment below the help article is dated ‘1 year ago’ …
met vriendelijke groet,