Why is my render screen blank?

I have been rendering for 90h without problems but it now has suddenly turned gray like this:

It says that the render is still going on as you can see on the taskbar but the timer has dissapeared along with the already rendered parts of image. Why?

In the top right it says slot 2, maybe you have different render layers or something, you should be able to see your image in slot 1.
Edit see this video explains render slots:

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Thank you so much! I thought I just lost 105 hours of render! (I am rendering low-poly but ultra detailed scene with 40k+ objects at 8k so that’s why it’s taking a while)

Yes I thought you might be stressed!