I am not sure what the issue is here; as long as you can access the GRUB menu and see Fedora and Fedora rescue option in the boot menu, then your GRUB is working perfectly and there is nothing to repair here.
If you can’t even access it then you need to repair it, using a tool like Boot Repair maybe.
If you actually have access to GRUB, then you should at least see these two options at boot time:
- Fedora Linux.
- Fedora Linux (Rescue).
The second one allows you to start a root prompt to fix any possible issues at your OS. However, since Fedora disables the root account by default, this option does nothing extra than your normal boot option (the first one).
Thus, you should try to enable the root account like this guide explains: https://docs.fedoraproject.org/en-US/quick-docs/root-account-locked/
Which will require that you chroot from a live Fedora system to your installed system and run the passwd root command on it to activiate it.
After that, you can go with the rescue option I talked about earlier.
Once you access the root shell, you can now run the first command that I told you to see what’s going on. You can also run some other commands to explore your system logs like systemctl --failed, sudo dmesg and journalctl -b. The outputs of these commands will help us determine the problem with your system.
Hope this helps! And you are most welcome.