I do not know of any issues with putting your store on vacation or upgrading your store. Neither of those events trigger any algorithm changes. When you return from vacation and start up your listings again there is a delay for the search engine to reindex your listings and that can last from a couple hours to a couple days, but you said some sales have coime in so it is safe to assume you are all reindexed.
I will let you know that your pictures are full of eBay picture policy violations though (click Link), although I( am sure you usded these pictures before your vacation so chances are this is not your main issue, I would still consider changing them to comply with the eaby policy. eBay has said within the last year they will start demoting listing with picture violations.
Not allowed
Including photos that don't accurately represent the item for sale.
Placeholder images used to convey messages, such as no image available, stock availability, or other marketing messages
Stock photos for used, damaged or defective items
Adding borders to your photos
Using a picture that is less than 500 pixels on the longest side
Adding additional text, artwork or other marketing materials to photos
Watermarks used for marketing
Watermarks that obscure or interfere with the item in the photo. We suggest that watermarks be smaller than 5% of your listing, and less transparent than 50%
Watermarks that contain specific information about your product or service
It is possible since you stopped your listing and then restarted then, during the reindexing they found this or other violations and have demoted your listing because of them?
Good Luck Selling!
@initeq wrote:I put my store on vacation mode and disabled purchasing last week for 4 days (mon-thurs).
I got home on Friday, and the next few days sales were fairly normal. I reached the limits of my basic $20/month store subscription, so I upgraded to the $60, 1000-listing subscription.
Since then, it seems like my sales have tanked. Yesterday I think I had 2 sales.
Anyone know of issues following either vacation or subscription upgrade? Is it maybe that the search algorithm is heavily weighted toward "sales momentum" and when that stopped for me (due to vacation) I moved to the bottom of the stack? Even if that is the case it feels like my sales are excessively low the past few days. Maybe something reset internally when my subscription changed so that even though my listing sales history appears unchanged, the system is ignoring it?
Thanks
When my husband and I go on holiday, I turn on the vacation mode, but I don't hide my listings. I just change the handling time to the duration of the vacation. Works every time and I come home to sales. 
