I am leaving mybidder and finding an alternative software.
I have been let down twice once last month,and today June 21,my snipe 8 UK pounds,winning bid 7 UK pounds

I'm sorry to hear that.
You did not include the item number in question or the status of your snipe, so you probably don't really here for a support (although the support is great).
If you still don't want to share this information, I could only guess that this is probably related to the recent eBay security issue when they requested all users to change their passwords.
Your Status field probably mentioned the same reason.

The sniper has no way to resolve it on its own, because you have to change and select your own password on eBay and then re-login into the sniper using your updated login information to keep it in sync.