problem with airdrop not seeing ipad

hi all, i was able to use airdrop without having a wifi device up until today. today i had to put my pocketwifi device on hook up my imac to it and my ipad to the device then airdrop could be used.

has some new protocol come thru that has prevented airdrop working directly from imac to ipad without a wifi connection? (have i just been lucky???)

also does this airdrop use my data download/upload from my service provider? ( i have limited data so need to watch my usage.)

thanks