Recently, we started receiving the error : Issuer should match tenants domainName for non federated identity when attempting to create a B2C user via a .net core app hosted in azure. No changes have been made to the configuration or code. The same setup and code is working in a different app pointing to a different B2C instance. The only differences are the specifics for tenantId, applicationId, etc.
I've compared the working instance with the non-working instance, and cannot find any configuration differences between the ADB2C instances, Azure App Services, security or configuration items, other than the aforementioned items specific to each instance.
I wasn't able to figure out exactly why this was happening, but I did find a resolution and thought I'd update this, just in case someone else ever runs into this.
For whatever reason, deleting the Azure App Service and recreating it resolved the issue. I used the exact same configuration as before and redeployed the exact same code. I'm no longer receiving the error.