If this is a licencing issue, demo mode is just as "unauthorised" as real money mode given that the aim of demo mode is to market the real money playing of the game. If the game loads in demo mode fine, but is blocked from real play, this is not a mere technical issue, this is a block based on a specific account group, such as "all UK accounts". It is most likely achieved by looking at the IP address of a real money player and refusing to serve IP addresses from a given region, hence the game not loading. In demo mode, there is less perceived need for this, so the game loads to an "anonymous" player, possibly because the game server isn't being passed any real money account to use with the game, so it doesn't know the IP address of the demo mode player.
Microgaming have had this more specific way of blocking players, and even individual games, based on country of access for some while. Canadian IP addresses can't load Playboy for example, but the game is there, and often shows up when not logged in. The UK licencing of software does indeed extend to the level of individual games, so it's possible that a supplier may block only some games because they have not yet been given the seal of approval from the UKGC, even though the software and platform are properly licenced.
