I've seen another post about this a couple of days ago but I'm not sure what I'm supposed to do to fix it. There is no message in chat when someone activates the excavator and no one is able to select a resource to mine. A message comes up saying 'excavator currently in use by'

I've assigned the neccessary permission to all players "oxide.grant group default excavatorlock.use"

can you show the ./data/ExcavatorLock.json file

try the "excavatorclear" admin command. It reset the data file

This is the data file. I did do the /excavatorclear command but it didn't seem to do anything sadly :(

{
"2815": {
"playerid": 0,
"displayName": "",
"captured": true,
"starttime": "2022-08-08T08:59:14.0048198+01:00",
"stoptime": "2022-08-08T09:01:13.977726+01:00",
"Name": "G6",
"PlayerCooldown": {
"0": "2022-08-08T09:06:14.0048198+01:00"
}
}
}

From what i see, it looks like you are using an older version of oxide with latest version of plugin.
there was a change in OnDieselEngineToggle parameters and if an older version of oxide is used with the latest plugin, it will not be called.
and this would explain the capture state, but no playerid.

/excavatorclear should display "Clearing the giant excavator status" 
if not, check permission and check config file if command name was changed.

Ahh okay, I'll update Oxide and see how it goes. Thank you