Tinkering around a bit.
On PC it gives me the "Your browser is not supported due to Unity Web Player limitations, please use other browser to start the game" Error message on Firefox, Internet Explorer seems fine.
I can log into it from iOS (Steam, Facebook, Google login options) and it doesn't give me an error message.
There is a huge amount of games on tabletopia but with a free account the choices are somewhat limited.
Also cannot understand it all that well. When looking for the Game manually it doesn't show in search results.
Only going trough the initial link i got from other Fleet-Commander fans it worked.
So it seems a bit undercooked at the moment, but that is the reason i asked for a patient victi...ahem...opponent.
I was thinking that it may be a cumbersome but good introduction to the game because it is mostly unknown but uimmenively satiisfiying game...also the other choices on tabletopia makes my mouth water.....
If you are interested I can send you the "invitation link" I didn't add it to public games yet without knowing the ins and out yet....
Set up and all is fine on my iPhone 6+ so at least that works out, don't know yet about the game itself yet, I cannot start it solitaire to test it out.