Hello,
The template preview is working fine in our test environment.
First, please ensure that you are using the latest version of the WPDM plugin.
If still, the problem exists then We’ll need to take a closer look to see why this might be happening. Therefore, I’d request you to check whether there are any plugins installed that might be causing this.
Here is what you can do to check:
Please try switching to another theme, like Twenty Twenty-one, and check whether the issue persists or not. If not, then it is the theme that is causing the error.
Deactivate all plugins temporarily except WPDM and see if that solves the problem. Then, activate the plugins one by one to see which plugin is causing the problem.
Try one more time after clearing your browser, website, and CDN caches if you have any. You may temporarily disable the caching plugin for testing.
.
