bad attachments?

so im mostly a lurker and love the 1 model a day thread but atleast 2 of the pdf wont download im running fox on a mac --ive also noticed the thumbs arent showing anything --i could stand to go from sierra to high sierra and fox did update to a new version but the pdf havent worked for a while (im not on daily only randomly) wifi seems no difference (home starbucks my phone teather think ive tryied it all)

any thoughts? i dont normally use safari in fact fox does really well--and what im seeing now: i tap pdf and loads black page try cmnd/s tryies to save as gif same if i tap and save as --but its a pdf file? and with cs i know i can use pdf