So if you want to use scope queries you can't have a conflicting function name.

When you created scopeWaiting laravel treats that as waiting(). Unfortunately, there is a naming conflict there. Perhaps change your scope query to scopeIsWaiting and then you can call it like User::is_waiting()->get()

I've come across this a couple of times, in most cases I have other where clauses or joins included in my query so I append the scope call to these further down the chain:

User::where('x', $y)->waiting()->get()

If you have no other clauses to attach to the query then you could do this:

User::query()->waiting()->get()

Looking at some of the cashier source code it doesn't look like they ever call the scope as the first clause it's always further down the chain.

Hope this helps.