pay small amounts but big amounts is still waiting for 5 days

I was trading as CopyFX trader with roboforex I attract some good number of investors and was able to make some good profits

I made a few withdraw requests of 100 to 450$ and it was paid pretty fast.
until the last time I traded and get a high commission of about 4600$ then I reuest a withdrawl of 450$ it arrives very fast then I request another 480$ and also I got paid within one bussines day, finally I request a withdraw of 3500$ and here the problems begins.
First of all the withdraw is still pending for 5 days now, from 28/12/2018 to 2/1/2019 and still pending.
my deposit and withdraw operations was stopped and I got a message in my account
Funds Withdrawal service is not available for you at the moment. Please, contact Technical Support for assistance.
I contacted the live support and they have only one reply "wait for the reply of your ticket"
now my ticket is with a high priority mark and didn't get any response for 4 days
this is completely awful

That's a very bad sign of something else anyway for whatever reason out there and I do hope it will really make them wonder for anything you may get there for something like that. I do not really want to do that for something else, but you may not get paid.