CiviContribute Donation Form error
We fixed this on https://chat.civicrm.org.

The latest versions of the Authorize.net eCheck payment processor extension (versions 1.2 to 1.2.2) break CiviCRM (the problem exists as far back as 4.7.23, probably further).

The solution for now is to disable the eCheck extension.  The author of the extension (or someone else - it's open source!) will need to fix the problem with the extension.