Level 18
The first result when googling "laravel session file 419" is this one: https://stackoverflow.com/questions/52583886/post-request-in-laravel-5-7-error-419-sorry-your-session-has-expired
I think the most likely cause for your problem is the one described in the first answer there, under "Possible error prone scenarios":
Probably file-based sessions might not work because of the permission issues with the /storage directory (a quick googling will fetch you the solution)