Sure, no problem. Context is I have a dual boot system. It had Windows originally, and I added Manjaro in October.
What used to happen
If I turn on my laptop, I’d see a screen with 4 options. Two options to choose either of the OS, one for Manjaro custom settings and one for UEFI options. I belive this is called the Manjaro bootloader screen (based on this page), but I may be wrong. It looked something like this (from the previous link), but I used to UEFI as the last option instead of Memory Tester:
Then if I select any of the two OS using cursor keys and press enter, I’d have reached the page to provide user credentials and that’s it.
While problem started yesterday morning, I was still reaching the above page. If I had selected Windows, no problem and everything was working as it should.
If I had selected Manjaro, then it was showing me the error that I shared in the main question.
What is happening
I applied what @GaVenga suggested in the evening. While I ran sudo update-grub, I received this:
I interpreted this as they removed the old entry for existing installation and inserted a new entry on top. I may have understood completely wrong, so sorry about that. Anyway, if I turn my laptop on after that, it is immediately going to the following page:
Let me know if this info is what you wanted.
So, I am not getting a chance to log in to Windows easily. While turning on the laptop, I have to press F12 to go to boot settings and from that Windows option is coming. This is just an inconvenience, which I am happy to ignore for now.