Okay Thank you !!
And one more thing I wanted to ask. When that error appeared I tried to download the latest plugins. But unfortunately, they aren’t downloading, the server error called “HTTP 500 Server Error” appeared.
I don’t think you need the Sentinel-3 images for this task. Keeping SNAP updated is good, but it is not required to install all possible plugins.
How do you get to this page actually?
By clicking on the download logo button on the bottom right, afterwards the error shows and there the download address is given and I manually open that address through browser.
Good News! The plugins are updated now. Actually it was an internal error that I have sorted out.