[Konstantinos]

Actually

pawn Код:

SetSpawnInfo( playerid, 0, 0, 1958.33, 1343.12, 15.36, 269.15, 0, 0, 0, 0, 0, 0 );
SpawnPlayer( playerid );

are awful on this part, because player isn't able to choose skin while the Register/Login is on Dialogs.
Just delete them and let players choose skin. After the "SPAWN" Button should work and spawn them.