If you are having problems sending account invites in the app, then you might be running into a new limit imposed by Shopify
Screenshot of the error shown in the app admin:
Shopify’s account invite limit
Shopify seems to have recently added a limit to the number of account invites that can be sent at a given time. This new limit has not been officially announced or documented by Shopify, but based on our testing the limitation seems to have been introduced around the beginning of June 2022.
You can only send 5 account invites within a 10-minute period
If you encounter the following error message while using the Customer Fields app, we suggest waiting 10 minutes before trying again.
Failed to send account invite
If you are still having issues after waiting 10 minutes, please don't hesitate to contact our support team via chat or email.
Merchants using Account Approval
If you are currently using Customer Fields for account approval, this will impact how many customers you can approve since the approval process involves sending an account invite. This applies to other staff users approving customers on your store as well, as the limit is specific to the store, not the user.
This is a limitation imposed by Shopify, so sadly there’s nothing we can do on our end to circumvent this issue.
If you would like to see this limitation changed in the future, we encourage you to reach out to Shopify Support.