Not sure why old Electrum version was unable to open my old wallet, but fresh install of 4.0.2 solved it.
That's because you've opened it using an updated version which also updated your wallet file.
The only way to use that wallet now is to open it with the same or
earlier newer versions of Electrum, trying to load it with an old version will result with an error.
Also, read the warnings above since you most likely downloaded a compromised version of Electrum v4.0+.
Or it may have failed to "
hack" because of your wallet's previous version, it this case, send the funds to a new wallet immediately.