Bought a brand new unlocked pixel 6a. Was aware about OEM unlocking being greyed out for the 6a. Updated to latest android version with all security updates done. Then factory reset and OEM unlocking was available.

Then went through web installer with no problem until the flashing process when this error occurred
"Error: The requested file could not be read, typically due to permission problems that have occurred after a reference to a file was acquired."

After this the phone boots with the bootloader unlocked but back into android 13 and OEM is not longer available to be unlocked. I tried factory resetting the device again with no updates to be done but OEM unlocking is still greyed out. So now can't finish the install and can't lock the bootloader either.

Does anyone have any suggestions? Using windows with correct driver installed. Any help will be much appreciated.

Thanks in advance.

I have resolved this issue. OEM stayed greyed out when the phone was on and the web installer wouldn't work at all. So I tried following the command line install on Ubuntu and this worked flawlessly and now I am fully installed with grapheneos and now locked the bootloader and OEM.

    3 months later

    Thanks Pointer3112 for the tip
    In the command line install it is also written to unlock the OEM, you skip this step and add no problem for the installation ?

    *add = had ^^ had no problem