Received 2020 CA state refund but not 2020 federal refund

Mailed my 2020 returns around April 2021 using certified mail.

Received my CA state tax refund in May 2021.

It is July and still have not received state tax.

I checked the "where's my refund" website and entered my SSN, filing status, and refund amount and it could not find anything.  What can I do?