Forum Discussion
Bing Maps API Authentication Error
Would you please consider moving this post involving API usage to the Microsoft Power BI Community Developer Forum, where they focus on the following: Custom visual creation, API usage, real-time dashboards, integrating with Power BI, content packs. Basically, everything about extending Power BI.
https://community.fabric.microsoft.com/t5/Developer/bd-p/Developer
As this is AUTHENTICATION, have you tried using HTTPS instead of HTTP? When you sign into your Bing Maps Portal you will see an announcement message that TLS 1.2 is now required and my assumption is that the connection for HTTP might not be secure enough to do the AUTH anymore.
If the issue only occurs with larger datasets, you are likely being ratelimited by the API. Basic Keys, free evaluation accounts, get a maximum of 5-20 QPS (queries per second) while Enterprise Keys, paid accounts, get 50+QPS depending on the API.
NOTE: I am a member of the Microsoft Maps Team and not Fabric or PowerBI so I can't speak to the Power BI or Excel side of this discussion, just the Map Auth.