Answer

If the failed sign-in is recorded in the Activity Log

• Make sure you are using the following setting in mt-config.cgi¹:

  TypeKeyVersion 1.1

• If you have upgraded but are not using the newest default templates, update the TypeKey sign-in links in your template to use the new shortcut tag for these. Using the new tag will force the TypeKeyVersion setting from mt-config.cgi to be applied for these links.

  So, look for any sign-in links in your Individual Entry Archive template, and replace them with:

  <a href="<$MTRemoteSignInLink static="1"$>"> Sign in</a>

  For simplicity, you may also wish to do the same thing for any sign-out links:

  <a href="<$MTRemoteSignOutLink static="1"$>">sign out</a>

If the failed sign-in is NOT recorded in the Activity Log

The reason for this error is an invalid timestamp on the signature, which occurs when the server time is incorrect. You'll need to contact your host and have them confirm the time is showing correct GMT on the server where your installation is located.

They can do this in Unix using the following from the command line:

date -u

If the output for that appears to be the correct GMT for the time at which the command was executed, they can then type in this (all on one line):

perl -e 'use POSIX; print strftime("%a %h %d %H:%M:%S\n",
  gmtime(time))'

If the second result is significantly different from the first, then that would be a further indication that the server is not reporting the correct time.

¹ In versions prior to 3.2, the configuration file is named mt.cfg.