It looks like the current version only works for eWay when the currency is set to Australian Dollars. Are you using eWay for a US merchant? If you change the currency setting to AUD then eWay will show as an option.
I see that both of your stores are using the same database. My guess is that caused the databases to not be updated properly and that is why eWay doesn't show. I could fix this issue, but I'm afraid it might imply there are others.
Can you try a clean install of PowerStore4 into a new database? Then we can work on transferring the old data from your other installation once the tables are in place.
What page doesn't display properly on mobile? If you give me the URL I'll take a look.