This is strange, I've looked at the reinvite code and I can't see anything really "wrong" with it, though in my experience I've never gotten the reinvite message if I accidentally or intentionally clicked the "no" button on when bot invites one of my toons to guest channel.
If the bot is able to invite you, it should be able to reinvite you. It appears to be the same function call, and if you're getting the reinvite message, you should be getting the invitation.
If you look in the plugins directory at the file vh_PrivateGroup.cs in a text editor and scroll down to where you get sent the reinvite message, you should see:
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foreach (UInt32 user in users)
{
this._database.ExecuteNonQuery("DELETE FROM pg WHERE user = " + user);
this._bot.SendPrivateMessage(user, this._bot.ColorHighlight + "You have been reinvited to the private channel");
this._bot.PrivateChannel.Invite(user);
}
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That's the only place I see the "You have been reinvited" message in the bot code. It seems to trigger for guest channel members who are not in guest chat every 5000 seconds. If you got sent the message, the very next thing that should happen is that you get sent the invite. If you look elsewhere in the code, the "join", "invite", and logon trigger all use bot.PrivateChannel.Invite(user).
If you're timer code above doesn't include the bot.PrivateChannel.Invite line after the bot.SendPrivateMessage, then that would be the problem.