Hello,
Thank you for contacting Rank Math and we are sorry for any inconvenience this must have caused you.
The credits you purchased opt to be added to your account. Can you please confirm if you can see the correct number of credits you purchased from here: WP Admin > Rank Math > Content AI:

If you don’t see the correct value above kindly check here: http://rankmath.com/my-account/websites.

If you can see the correct number of credits here like in the image above, but not on your site then this is a problem with the syncing of information between rankmath.com and your website. Disconnecting and then reconnecting your account should mostly resolve this.
Kindly follow these steps:
You may try disconnecting and re-connecting Rank Math to see if that works for you.
You can disconnect your account by navigating to WordPress Dashboard > Rank Math > Dashboard > Help and then simply disconnect the account by clicking on Disconnect Account.

Once you’ve disconnected your Rank Math account, you can connect it again in the same settings. In order to connect your correct account, click on Connect Now.

Once you click on Connect Now, please ensure that you’ve selected the correct account and then click on OK, Activate Now.

After doing this, refresh the credits to start using Content AI. Please head over to WordPress Dashboard > Rank Math > General Settings > Content AI and refresh the credits.
Here’s a screenshot for reference:

We hope this helps you. Let us know if you have further questions
Thank you.
Hello,
Since we did not hear back from you for 15 days, we are assuming that you found the solution. We are closing this support ticket.
If you still need assistance or any other help, please feel free to open a new support ticket, and we will be more than happy to assist.
Thank you.