TestFlight - can't Install my App

I have been using TestFlight since before Apple bought it and this is the first time I am not able to install my App. Steps: - open TestFlight - tap Install - the load icon ( the circle) appears - then, before it starts to show and data load the load icon disappears - and the Install button has come back - then get error message 'Unable to download App. App can t be downloaded at this time.' I have tried: - reinstall TestFlight - reinstall my phones default settings - delete and re-add my internal testing ID No go !