3D FlipBook - Please wait! The book is processing... pdf.worker.js?ver=4.3.136:23 Uncaught TypeError: Promise.withResolvers is not a function

I get the "Please wait! The book is processing..." which never goes away which is because of this error I believe.

Here is the full error from the Dev Console:

pdf.worker.js?ver=4.3.136:23 Uncaught TypeError: Promise.withResolvers is not a function at pdf.worker.js?ver=4.3.136:23:1431038 at pdf.worker.js?ver=4.3.136:23:1432101 at pdf.worker.js?ver=4.3.136:23:1432328 at b._onComObjOnMessage (pdf.worker.js?ver=4.3.136:23:1411925)

I fixed this once about a year ago by uploading a clean version of the plugin, but that no longer works.

I have set up an EXACT DUPLICATE dev site of the live site should you wish to login to replicate the error youself as well as debug. I see that;s often your reply to other support requests around this issue. Let me know if you have a preferred username/password and I'll create a user.

Note: My temporary fix to remove this error is to revert the plugin back to version 1.11.1 - no issues with that version.

Steve