Moto Droid error 408 on wifi works on data

Question

I have a Moto Droid Zoiper register on Data but not on wifi.  I tried it on another android phone a Galaxy Note 4 on the same wifi and it worked perfectly, but in this other phone Motorola Droid it wont work on wifi.  I tried another Moto Droid from one of my coworker and the same thing it work on Data and it wont work on wifi.