question about joining server

when i join the server it says" you cannot play/edit this mission it is dependent on downloadable content that is missing or deleted. buildings3"
it still lets me play though so i dont know what im missing because i checked and i have files marked buildings3

Disregard said message

just click through it.

It's an Arma thing.. I believe it has something to do with you not having the british ops DLC installed, which is 'supposed' to be a requirement for a mod we have installed.. but it's unneeded.