cannot change file association

This is a general bug.. with some possible workarounds (maybe):

I used Google to search for
can't change default program build 1803

Version 1803 does not allow me to set defaults by app - MoBEX error Solved - Windows 10 Forums
Default Program Settings - Microsoft Community
file association - Windows 10 removed the option to - Super User
Today I noticed Win10 1803 we're unable to set some apps as default (Notepad++) : sysadmin

for example. Different flavours on the changes MS have foisted on the unsuspecting public - er - I mean improvements they have delivered to their customers.

I would have thought it should be possible to use a 3rd party program such as the Default Programs Editor
Default Programs Editor

(run as admin)
to effect some changes in the registry for simpler cases at least, if there is no way using the Windows GUI.

Accuracy and confidence required, but it does support defined tasks.

Similarly with Filetypesman - making the changes manually.

In both cases the question would be whether the changes can be written to the registry- and retained on restart, for example.

Glad I stayed with 1709...

Cumulative Update KB4462919 Windows 10 v1803 Build 17134.345 - Oct. 9 - Page 2 - Windows 10 Forums

I can find nothing about that in the comments following that update- but it may simply not have been mentioned there.
Do you have a source for that?

Comments on that here:
After CU KB4462919 W 10 v1803: can you change default program?Y/N - Windows 10 Forums

Seems the update only applies to 1803, 1809 as far as I've found so far, and I haven't had it on 1709.

Thanks.

You could try uninstalling the update.....

Updates can be hidden so they don't recur; however any next update will presumably incorporate the same change, unless the update has been corrected (I was going to saw updated!).


Hide or Show Windows Updates in Windows 10 | Windows 10 Tutorials