Previously working widget now returning invalid plugin token (Err 2)

Hello,

I have had a widget up and hosted for about a month now and it has been working flawlessly. I've not touched the code for it, but despite this it has stopped working and suddenly returns an error instead.

When loading a page hosting the widget the widget now says "Invalid plug-in token (ERR2)"

And the terminal states a very similar problem, but with slightly more detail referring to JWT.
https://i.imgur.com/AsxQpkn.png

Any help would be appreciated.