Hi @Bryan-Square we are still experiencing the same issue, upgrading from 25.1.0 to 26.0.0 and above, any call to Square freezes/locks IIS and VS.
I can create a completely blank web project with nothing in it except the Square API, debug the application in localhost, make any call to Square and it freezes.
If I use a Windows Console Application upgrading from 25.1.0 to 26.0.0 and above it works correctly so suggests this is some issue running the API on a local web server.
Just an assumption but the library APIMatic.Core was used in the upgrade from 25.1.0 to 26.0.0, could it be something to do with this library?
I also added this comment to the thread here that appeared to be having the same issue: