Confused

I tested cyanotype exposure time this afternoon ahead of a workshop on Tuesday (fingers crossed for reasonable weather). And this sheet of paper (from the last batch I made up) hardly changed colour in an hour and a half. An older sheet then exposed normally in about 1/2 hour (at approaching 4pm). Will need to retest this new batch of papers tomorrow, as I am wondering what I’ve done. If any blippers who cyanotype have any ideas please let me know.