Outlook PDF preview error

Hello

I have W11, and Outlook 2016, and my previewer has stopped working. 

message: Outlook PDF preview error: This file cannot be previewed because there is no previewer installed for it.

I followed the instructions at https://support.microsoft.com/en-us/office/outlook-pdf-preview-error-this-file-cannot-be-previewed-because-there-is-no-previewer-installed-for-it-b78bfe24-ba13-44bd-8289-1919ece7ded2 but Outlook & Adobe Reader are both 64 bit.

I didn't have the PowerToys App but I installed it in case it would help. No Joy.

Advice where to turn now, please. 

Cheers Gibbsy