TSP enrolled but no Achievement Code access (no Request button visible)

You should have received access within ~24 hours so this does sound like an issue. Unfortunately, the quickest way to resolve is repeat the onboarding process with a new email address. Instructions for onboarding can be found in our Get Started materials (https://aka.ms/GetStartedTSP). Look for the file titled "Microsoft Learn Achievement Code Onboarding and Usage Overview".