Update your plugin, you're using an old version.
Note: auto external host method is not working anymore because the hosting platform I used now closed because they are now out of business.
I do not own that the Ploud hosting business so I can't do anything against its fail.
I suggest you to start using self host and read more about it in the official guides: https://itemsadder.devs.beer/plugin-usage/resourcepack-hosting
I'm working on a new auto external host but it will require time.
Thanks for the patience, I sadly have no control over this issue.