I am creating an atlcoin cloned from litecoin (version 0.15). The genesis blocks are mined and I have setup two nodes on VPS that are connected to each other. I can mine new blocks and sync them with each other perfectly on the regtest network. Unfortunately I am unable to do this for either the mainnet or the testnet. I am stuck as the nodes are not syncing with each other. I have mined coins on one peer but they are not downloading in the other one. I get the following message in the debug.log file

2018-01-08 06:20:39 Timeout downloading headers from peer=2, disconnecting
2018-01-08 06:20:41 receive version message: /GlobalcoinCore:0.15.0.1/: version 70015, blocks=3, us=165.227.36.100:19335, peer=4

Any idea why they are not syncing on the regtest but not on either of the others? Any help would be greatly appreciated!

Thanks! The latest version is 0.15. Any reason you have opted for the old release of 0.8.*? This would imply that you are missing the recent security fixes/upgrades in 0.15.* (since 0.8.*) Litecion code base

Does Poseidon have the capability to support Segwit and Lightning networks? Which version of Litecoin have you forked from? Seems dated