It isn't the kind of experience I want you to have while working with QuickBooks Desktop (QBDT), @Deacon1. It's my goal to help you create customer letters using Microsoft Word templates within the Customer Center. I'm here to share some troubleshooting steps to fix the error you're getting.

As I've checked from your screenshot, I can see that the digital signature has been revoked. This can be the reason why the system hinders you to create custom letters for MS Word. Please make sure to install the QuickBooks Desktop Security Certificate to isolate the issue.

Here's how:

1. Locate the file.
   1. Right-click the QuickBooks icon on your Desktop and select Properties.
   2. On the Shortcut tab, select Open File Location, then OK.
2. Install the Certificate.
   1. On the File Location window, look for the Application file (.exe file), then right-click and select Properties. The Application file Properties window opens.
   2. Select the Digital Signatures tab and choose one of the entries in the Signature list field. Select Details.
   3. On the Digital Signature Details window, select View Certificate. The Certificate window opens.
   4. Under the General tab, on the Certificate window, select Install Certificate.
   5. On the Certificate Import Wizard welcome screen, ensure that the Store Location is on Current User, then Next.
   6. On the Certificate Store window, Windows already selected the certificate store based on the type of certificate. Select Next, then Finish.
   7. You will be prompted that the import was successful, select OK.

I'm also adding this material for additional reference: Add QuickBooks Desktop Security Certificate manually.

If you had the certificate installed, make sure that your QuickBooks Web Connector is up to date and that the third-party digital signature is valid. You can review the resources from this link as your guide: How to fix the error “QuickBooks - Application with Revoked Certificate”.

I'm more than happy to help if you have follow-up questions while working with your customer letters. Just leave a comment below. Have a good one!