This quote from Paul leads me to believe that AmSnag is a web scraper not tied into Arrow via API:
I noticed that what I referred to as the backup was unable to retrieve fares; but at least the slower, original one was working. But now it hanging.
I have time; and I will see if I can figure out the problem. Recently Amtrak's fair finder webpage was changed, the second time during amsnag's lifetime (I recall several AU threads complaining about it). As I mentioned, the original version was still working for a while; and if you clicked through to Amtrak, you got the prior version's page with the search results.
It's possible that Amtrak pulled down the prior version, which would kill amsnag and require starting from scratch.
But one can't put in a 30 day chunk of time to check fares on the Amtrak site like one could/can with Amsnag, correct? That was/is the main point of Amsnag, wasn't it?