I have the same issue with the re-release of 1809 on Dec 3.
I have applied 2 cumulative updates for 1809 since and still cannot set up swap on a non-O/S drive.
When does Microsoft expect to release an update to fix it?
I did Microsoft updates on Dec 3.
When I re-booted the message came up.
I have seen several others complain of the same issue after 1809 update.
Seems you can no longer use any drive other than C: (or possibly your O/S drive) for virtual memory.
I had a 30 Gig page file on my F: drive and the update deleted it and created the temporary pagefile on C:
Every time I re-create the F: drive pagefile.sys, the O/S deletes it on re-boot and creates the temporary one.
Although it deleted the pagefile.sys on F:
It still shows in the performance, advanced GUI interface used for setting the virtual memory; that 30 Gig is still set on F: (as I set it originally)
After It created the temporary page file, the GUI interface it still indicates that there is no virtual memory on C: (as I set it originally)
So I have set windows to manage the pagefile on C: and await for Microsoft to fix their O/S.