Most likely the status of your profile is not "Active". Meaning if you have just registered and administrator of site didn't yet activate your profile. If you have used dating services for a while then you must have changes some info or put new photos on. After that your profile still was to be checked by administrator. Usually it doesn't take more then 24 hours. As soon as your profile is active you can send and receive messages absolutely free. (More info on profile status you can read on page 2.10)
I had the same problem.
If you have a router from TP-Link, D-Link, ASUS or maybe a router produced by some other companies
then this is a problem with a router.
There are two ways to solve this problem:
1) Upgrade firmware for your router. You may download the last version of firmware
from website of the manufacturer of your router.
2) Change "MTU" value to "1400" in your router settings.
This option is located in "IP Config" -> "WAN & LAN"