By searching of this error I found that some users reported same thing in 2017. The reasons it occurs is mostly because of outdated Electrum version or OS which is missing some file required for the proper functioning of Electrum.
Users of Windows 7 need to install KB2999226 Windows update, some
report that they solve this error after update. There is also report that
corupted wallet file can also cause such error, and that problem can be in
Pyinstaller.
If none of the above does help, it would probably be wise to make clean install by deleting Electrum folder with all files, and restore wallet with seed.