Can't run and jump at the same time on my server.

I own a Darkrp server, and for some reason players cannot run and jump at the same time. If you wish to run and jump you must stop movving and click your jump button (space) 3 times.
Please help
Thanks in advance,

same problem help please

Ah I know how to fix it, if anyone else is having this problem change your server tickrate to 66 or 33.