airdrop problem

i have imac 2011 and macbook pro touch bar 2017 ipad pro and iphone 11 pro the imac 2011 is the one refusing to connect to anything via airdrop

i did fallow steeps in videos in youtube but in my imac it doesn't show the options of allow my imac to be discovered

my imac is 2011 , 2.5 inch running on high sierra 10.13.6

please see the photo attached any help is appreciated

regards