DONOTCACHEPAGE defined. Caching disabled. issue

hello developers,
would like an asssistance with this issue as stated above. i have previously installed your plugin in two different website.

as i test cache for both, one shows no problem at all, the other one shows error message “The pages do not match! Timestamps differ or were not found!”.as i check the log, one of the line shows log text as above – “DONOTCACHEPAGE defined. Caching disabled.” so far the only cache plugin i have installed is this one. so would like an asistance onj what should i look into to address this issue.

thanks in advance