It won’t let me spend my apple credits

I have money in my apple credits

If you mean you have add funds to your Apple ID balance, it would take about 1 to 3 business days.

Check again after a few days, see -> Check your Apple ID balance

Check your Apple ID balance – Apple Support (UK)

See also ⤵️

Add money to your Apple ID balance

Add money to your Apple Account balance - Apple Support (IN)

Change, add or remove Apple ID payment methods

Change, add or remove Apple ID payment methods – Apple Support (UK)

 -> set your Apple ID balance as default payment method.

Payment methods you can use with your Apple ID

Payment methods you can use with your Apple ID – Apple Support (UK)

If you're still unable to update your payment method, Contact Apple Support.

Get more help:

Call Apple in your region see: Contact Apple for support and service

Contact Apple for support and service - Apple Support

or -> Contact Apple Support -> Get Support (apple.com)