I have the same issue and have reinstalled MachForm 3 times now (including destroying and rebuilding the database prior). I am able to login after the install using the default password of 'machform'. I just don't want to leave the default password in place, so I immediately log in and change it. Then, I attempt to log in with the new password I just created and it pops back to the login screen.
Planning to uninstall and reinstall one more time. Then, I plan to reset the password without using special characters and all lowercase (like the default password). Just a guess, but none of my other guesses have worked so far.