ACTUALLY THIS IS NOT SOLVED AT ALL... I apologise for my lack of response to this thread, but I never got any notifications for it, I had even forgotten that I had posted it, the only reason I'm here now is because I googled the problem & my post came up, lol.
The issue I had previously only got fixed once our server provider moved our server from the West coast of the US to their East coast location, instantly after the transfer, I was able to see the server once again & able to join. The server move was not done because of my issue, it was done for an altogether different reason, my connection issue being solved was just a curious bi-product of the move.
The reason I am back here now is because I have suddenly developed the same problem again, this time for a public server I was attempting to join. It was showing up fine with 90 ping in A3L, the launcher told me I had to download some mods to play on the server, so I did that, but afterwards the server was suddenly showing as 9999 ping and I cannot connect to it. Even weirder... it now no longer shows up in my dedicated Arma 3 browser list too.
So if anyone did actually manage to find a fix for this problem, please don't hesitate to post it here. Many thanks. (this time I will be monitoring this thread).