Strange Popup

Hi all,
for the last week I get the below popup about 2 to 3 times a day.
any one know what is going on?

The default app you have set for epub isntworking so its resetting it what have you get set to open epub?

This means that something has tried to change one of the file association settings by a method not approved by Microsoft. Often this is due to using old software that uses methods of manipulating the registry settings that were once allowed but are now deprecate by Microsoft.

It can be difficult to identify the culprit because the app association being reset often bears no obvious relationship to the program that triggers the reset. Also, the reset may nnot occur when you first open the program, it often only happens when you use a part of its features that access the file associations. The 'File.. Open...' operation can do it.

Once the 'guilty' app has been identified, the problem can often be cured by installing an updated version.

As an example, here's a thread where an older version of Irfanview was the culprit and the latest version was the cure.

Setting up Windows 10 Pro

Thanks to both of you.
I found the place where you can set the association, as soon as I opened it, I got about 20 of those popups. some where from the windows program Photos. most of them went by so fast I could not see the extension that was doing this, but 2 where from Photos. Now that is a windows program installed with windows. Did this happen during an upgrade? I don't know what to do next, or do I need to do anything at all?
Thanks
Sven

Sven1458 said:

I don't know what to do next, or do I need to do anything at all?

Set the association as you wish, and just keep an eye out for it happening again. It may well not happen again, but if it does note what program you were using at the time, it may need an update. Photos and the other Microsoft-supplied apps won't be triggering it, but some (particularly older) third-party apps may.
.

Most of the time this happens, I was in Edge, surfing, as seen in my attachment.
I keep an eye on it.
Thanks
Sven