You should probably just host a server and then just connect your self to that server. Play Solo opens the studio mode/ studio (in 1.3) and you can't talk in old roblox studio. The expirmental build fixes this by making you join a self hosted server when you click play solo.
just host a solo server or use networkclient (not recommended and only for clients 2008M and below and can do serversided glitches like hopperbin rocket bullets falling without any force)
