Error installing OpenMTBmap UK

Sorry I need help and my english is not good.
I loadet with Great Britain on my PC but when I want to open this I got a message …Installer integrity check has failed…more at
But the Swiss map was no problem. The file is only 2 MB is this OK?
Than I lodet Great Britain wit open street map and now I have it on my Map Source.
When I mark the map and say, send it to my Oregon 300 it need a long time but finaly there is a message, is OK
When I start the Oregon the say… Cant Autenticale Maps, an even part of mx Topo Austria are gone.
Garmin Graz, Austria, say thats a problem with open street map sorry!
What shall I to?
Please help.