So, I used the downloader the first time; works perfectly: files generated, zipped, and downloaded properly. I went through the same process again (with different data), nothing: same filename, same files in the zip. Access logs show the first GET, but none after. There's nothing in the error log.
134.197.0.23 - - [24/Jun/2021:17:49:25 +0000] "GET /pick_sources.html HTTP/1.1" 200 683 "http://erinkeith.pythonanywhere.com/program_source_importer" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.060
134.197.0.23 - - [24/Jun/2021:17:49:30 +0000] "POST /pick_sources.html HTTP/1.1" 302 243 "http://erinkeith.pythonanywhere.com/pick_sources.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.039
134.197.0.23 - - [24/Jun/2021:17:49:30 +0000] "GET /pick_columns.html HTTP/1.1" 200 5856 "http://erinkeith.pythonanywhere.com/pick_sources.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.021
134.197.0.23 - - [24/Jun/2021:17:49:42 +0000] "POST /pick_columns.html HTTP/1.1" 302 243 "http://erinkeith.pythonanywhere.com/pick_columns.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.036
134.197.0.23 - - [24/Jun/2021:17:49:43 +0000] "GET /pick_weights.html HTTP/1.1" 200 80802 "http://erinkeith.pythonanywhere.com/pick_columns.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.175
134.197.0.23 - - [24/Jun/2021:17:49:53 +0000] "POST /pick_weights.html HTTP/1.1" 302 253 "http://erinkeith.pythonanywhere.com/pick_weights.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.002
134.197.0.23 - - [24/Jun/2021:17:49:53 +0000] "GET /generate_rankings.html HTTP/1.1" 200 818 "http://erinkeith.pythonanywhere.com/pick_weights.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.008
134.197.0.23 - - [24/Jun/2021:17:49:56 +0000] "GET /downloader HTTP/1.1" 200 2305 "http://erinkeith.pythonanywhere.com/generate_rankings.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.921
134.197.0.23 - - [24/Jun/2021:17:50:38 +0000] "GET /pick_sources.html HTTP/1.1" 200 683 "http://erinkeith.pythonanywhere.com/generate_rankings.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.041
134.197.0.23 - - [24/Jun/2021:17:50:45 +0000] "POST /pick_sources.html HTTP/1.1" 302 243 "http://erinkeith.pythonanywhere.com/pick_sources.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.040
134.197.0.23 - - [24/Jun/2021:17:50:45 +0000] "GET /pick_columns.html HTTP/1.1" 200 6271 "http://erinkeith.pythonanywhere.com/pick_sources.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.093
134.197.0.23 - - [24/Jun/2021:17:50:55 +0000] "POST /pick_columns.html HTTP/1.1" 302 243 "http://erinkeith.pythonanywhere.com/pick_columns.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.050
134.197.0.23 - - [24/Jun/2021:17:50:55 +0000] "GET /pick_weights.html HTTP/1.1" 200 80607 "http://erinkeith.pythonanywhere.com/pick_columns.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.101
134.197.0.23 - - [24/Jun/2021:17:51:08 +0000] "POST /pick_weights.html HTTP/1.1" 302 253 "http://erinkeith.pythonanywhere.com/pick_weights.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.003
134.197.0.23 - - [24/Jun/2021:17:51:08 +0000] "GET /generate_rankings.html HTTP/1.1" 200 732 "http://erinkeith.pythonanywhere.com/pick_weights.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.101 Safari/537.36" "134.197.0.23" response-time=0.001