See "Web Interface - Settings - Miscellaneous - Tamper Detection" for a complete explanation of MOVEit DMZ Tamper Detection.
This button found on the linked page resets the cryptographic start hashes of all organization's tamper-evident chains.
There is a system-wide "on/off" switch for MOVEit DMZ's tamper-evident features. The page available through this link flips this switch on and off.