Thanks Mike, i tried the sign in, sign out still the same.
It’s okay perhaps its the file itself is somewhat corrupted.
What happens if you open the ruby console [menu] Extensions > Developer > Ruby Console and then try to open a new file?
Is the problematic sample file same as this here ?:
Sefaira Example Models – Sefaira Support
Try to download that and check…
Other idea:
Do not click in the graphics area. (Because that will loose the focus from the possible off-screen window) But try to use the Alt-space method above, to see if there is an off-screen window.
Or
Hold down ⊞Win +Shift
and hit ← (repeatedly)
(Windows Key + Shift + left Arrow key )
If there is a “missing” windows, then this should move it “circularly” between multiple monitors.
Something else to check, I wonder if the sefaira plugin is trying to open a web browser and it is being blocked by as a popup.
Only a guess as I have never even tried Sefaira.
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Sorry what do you mean, do you have the open file cmd for Ruby?
Typo. 
Try to download that and check:
Download that file, and try to open that one to see if it is behave as your “problematic” file.
Doesn’t work, its okay. Thanks for the help.