Pool chlorinating liquid is a commodity that retailers will only buy so much of and then not restock until next season. We are getting sporadic reports that many of the big box stores are out of stock and are focusing on stocking fall products (like back to school stuff). In warmer climates like the west coast and south, retailers will usually have longer supplies or more consistent supplies because the pool season is longer. In Vermont, you would be better off stocking up in the beginning of the season to avoid supply disruptions. Also, if your CH is the proper range, you can use calcium hypochlorite to chlorinate your pool OR maybe find some “cleaning” bleach (low % bleach with no additives) and use that. Check farm supply stores or industrial cleaning suppliers as they often have high concentration liquid chlorine in stock but you usually have to buy in bulk.