My main gmail account can't log into Microsoft store, but my other gmail can.

For this scenario, the issue is specific to one Microsoft account sign‑in, not to the Store app or Windows itself, since another account works.

Use these steps focused on the problematic account:

1. Run the Microsoft account sign‑in helper
   • Go to the Microsoft account Sign‑in Helper tool: https://go.microsoft.com/fwlink/?linkid=2214157
   • Follow the prompts for “I can’t sign in” with the affected Gmail‑based Microsoft account.
   • If an error such as Error 400 is reported, follow the specific guidance in the linked article for that error.
2. Check for general Microsoft account sign‑in problems
   • If the account has other sign‑in issues (for example in a browser or other Microsoft apps), use the guidance under “Additional help for Microsoft account sign-in issues,” including:
     • Reviewing any error 400 guidance if shown.
     • Using the account recovery form if sign‑in is blocked more broadly.

If the account itself cannot be fixed or recovered through the automated tools, the Store will continue to fail for that account while still working for others.

References:

• I can't sign in to my Microsoft account
• Microsoft Store doesn't open