Directive 'UseDNS' is not allowed within a Match block

This occurs when sshd configuration has been modified to include Match blocks and the directive is not supported as part of the match. There is no way to explicitly end Match blocks (note: see solution 2 below for one way to work around this). From the sshd_config manual page:

If all of the criteria on the Match line are satisfied, the keywords on the following lines override those set in the global section of the config file, until either another Match line or the end of the file.

Solution 1:

Match blocks need to be at the end of the sshd_config file, and all global configuration options must occur before these Match blocks.

Solution 2:

Another option is to have a line with nothing but Match on it, which effectively matches everything and therefore is the same as 'ending' the block.