I couldn’t solve the issue, but it got solved automatically anyways.
I tried updating the Hestia, and tried restoring a backup too… Unfortunately none of them worked, and lost my hope on getting it ready.
But maybe a week later, I opened the Hestia Panel, and to my surprise it was working again. I don’t know what changed between thoe two points, but the only thing that got to my mind is that I had upgraded my server storage some days before, due to low storage.
So, although I’m not sure of it, I think maybe Low disk space might be the reason the panel stopped working, and if anyone else gets this issue, and can’t find any solution, please do check your disk storage.