It is likely that you have ...
Published by Jeremy Biddle, Engineering Director at Bluewater Bio
It is likely that you have got elemental sulphur deposited in your scrubber, due to incomplete oxidation of the hydrogen sulphide. Instead of forming sulphate, it stops at solid sulphur (yellow colour) and its not easy to get rid of once it has formed. Best to replace the media if you can.
If this is indeed the cause of the blockage, the reason it has formed will probably be that the pH of the scrubber is too low (acidic/neutral). H2S scrubbers should operate at pH > 9.