No shares accepted

I have a pair of old USB Dragon scrypt miners, they have one GC3355 chip inside.
both sticks working together give about 500KH/s.
This USB sticks come bundled with cgminer 3.1.1 modified for them.
I was using them without a problem on another miner pool, now I moved to Prohashing.
The thing is that no matter how I config, I never get any shares accepted.
Everything seems to work fine, but shares are never accepted.
I tried with difficulty 512 and 1024.
I also tried setting one specific coin, first LTC, then tried trinity because I supposed the difficulty would be less, nice for using this old miners.
But never any valid share accepted......

Any ideas?
Help is greatly appreciated.

the password field I tried included:
a=scrypt
n=miner1
d=512 or d=1024
c=litecoin or c=trinity or no c at all

so for example one of the combinations I tried is "a=scrypt n=miner1 d=512"

You may need a newer copy of CGminer also, but the initial difficulty set by the pool means the low hashrate of that setup will take days before it will produce a share. I would advise against it, it likely will not be profitable.

Hmmmmm so the difficulty for the first share is 65535, and then it is set at the value you programmed for the next shares?
As for profitability, I have the notebook turned on anyway most days, and that two sticks only use 5 watts each.
But if it can take days for getting the 1st share, that IS a problem.....

This is very sad, this mining pool looks very nice to me, I was in another mining pool and moved here.
Now it looks like I can´t mine here at all.
On the other pool I was getting say 5K litoshis each day, I know it is nothing, but I also have a broken Gridseed board that I plan to repair and add to this two USB sticks to get a bit more hashing power on my side in the near future
I really will like to stay here.

maverick528 wrote:This is very sad, this mining pool looks very nice to me, I was in another mining pool and moved here.
Now it looks like I can´t mine here at all.
On the other pool I was getting say 5K litoshis each day, I know it is nothing, but I also have a broken Gridseed board that I plan to repair and add to this two USB sticks to get a bit more hashing power on my side in the near future
I really will like to stay here.

You'll still earn the same amount of money as you would at the other pool; it will just have a lot more variance than you had there. You'll see large amounts of money credited infrequently, because the difficulty is so high.

TYVM Steve for your answer, but mining for example 12 hours without a single share accepted is a waste of time, and its depressing.
I know small miners like me are not a priority for any pool, but maybe you can consider adding a "channel" with a lower diff.
Say, prohashing:3334 with a static diff of 1024 for example.
And with the answers Im getting here, maybe Im wrong but Im understanding now that the difficulty d= command in the password field is not working at all.