I've looked into this coin for some colleagues of mine and found some issues.
First, upnp is disabled in the code itself, meaning clients can't connect to each other, only nodes - of which there currently only seems to be one that is active. I fixed that code and recompiled the wallet, but either that one node isn't relaying peers or nobody else is running the coin with a connection to that node.
ah, it seems like upnp was actually turned off. thats a mistake, fixed that. although its not turned off in the code though, it is a compiler argument. but the rest of the explination is a bit off. UPNP maps port forwarding for you, otherwise you have to do it manually. it doesnt prevent you from connecting to other wallets. if you manually port forwarded (i do that with all my wallets manually anyway so i guess i never noticed upnp was off) then upnp wont do anything.
Also a client and a node are the same thing. i guess the distinction you were making here is if one had port forwarding done or not though.
Second, the old wallet issue is a simple one. The reason you get an error when you try opening an old wallet.dat is because of the 0.2 versioning. The old wallets were 1.0+ wallets, so when you try to open an old wallet, it thinks you're trying to open the wallet with an old client. Fixed that.
just run upgrade wallet= whatever the wallet version is to fix that. i already coded a fix for that without compromising the integrity of the feature structure of the wallet upgrade system. so upgrade=20500 would fix it. or if you have 0.2.4.9 then you run upgradewallet=20409. i made a post about this i think on the last page.
Third - Yesterday I had a colleague send a large amount of coins to the exchange with the custom wallet I had to make for him because the one made by the dev cannot open old wallets (see above) and they were never confirmed despite showing up on the then functional block explorer. However, I was able to send a small amount of coins (1000) to the exchange from the same wallet afterwards, and they *were* confirmed by the exchange.
sounds like your colleagues wallet might have forked itself? unsure. would have to have debug logs to tell. although that is possible.
Fourth - The node that is online is not relaying blocks from the chain, making it impossible to sync. I expect that this is the same issue the explorer is having.
I've found all the issues I have encountered to be obvious from a coding perspective and the fixes trivial at best. I don't know anything about the state of the chain, or why the nodes have stopped relaying blocks. So take all this for what you will.
the three seed nodes are relaying blocks just fine. the explorer is actually disabled completely right now because they are upgrading wallet versions. one of them did crash for a little bit though
to address the, why can i not sync? issue. the best remedy is to try to rebootstrap and sync again. usually fixes the problem (or sync from scratch but wait a while)