Mac stuck at loading bar, doesn't start
Maybe you have a problem with the internal private ram used by the system so it cant’ boot up. You can try this manipulation (2 or 3 times to be sure).

If it doesn’t work, try booting your Mac without extensions (as explained here).

If it still doesn’t work maybe you can try to install macOS from the recovery partition to an external hard drive and then boot up by maintaining alt before the Apple logo. If it works maybe you have a problem with your hard drive or the partition table (GUID) and if it doesn’t work it’s most certainly a hardware problem.