Two persons we know of have contacted us after not being able to back us, which is sad.
They both have succeeded now, a good tip is to try to do it from a computer if you can't do it in the app.
This is the response we got from the Kickstarter team. So please don't give up :-)
I took a look and it appears that your project page is working normally.
Backers may report issues pledging for a number of reasons. It's generally best to have your backers review our FAQ resources, linked below, and then try their pledge again (perhaps in a different web browser). If they're still having issues, they should reach out to us directly so we can look further into it.