Now working properly
I fiddled around with it more by turning test on and off in the site and payment areas and on Authorize.net and finally got the data hitting authorize.net from the Powerstore last evening. So, like smacking a vending machine, I don't know what the problem was or how it was fixed, but I did finally get my bag of chips.
I appreciate your quick response here on the forum and the offer to create a ticket. If it stops working again I'll be back in touch. meanwhile, thanks to Webassist for all the great extensions and products.