This may be a labor board issue about wages,vacation pay owed.The main thing is to get your claim filed,approved and paying. That could take some time by itself . Then start the proccess for backdating claim. I am sure you could make a case that you tried to contact them for weeks for guidance on when to file. Hope you have documents on being laid off and vacation pay owed.
Many companies are closing now since the Government money ended, your seperation could be covid related in a business aspect.
File the claim by Friday ,cut off is Saturday. I know in the past that the week you filed is when your claim started. They will still ask you last date worked and have options to put in with your reason for seperation.
If they are going to burn you on vacation pay ,they may hold up your claim to avoid paying EDD ?
This link is about how to request a backdate on claim, you will also be able to send a message from your EDD mailbox.
https://www.edd.ca.gov/about_edd/cor...tm#collapsePUA