Gray Tank Smell (Seriously annoying)

FIXED IT! There were one or two comments about the vent pipe not protruding high enough… after taking the vent cap off for the 5th time in the last several months, I noticed that it was under the roof line and that the hole that was cut out for the pipe was not done very well leaving large gaps of space between the roof and the pipe. I ripped the base of the vent cap out, and replaced the entire setup with a Cyclone https://www.homedepot.com/p/Camco-Cyclone-Plumbing-Vent-Black-40597/309587984?source=shoppingads&locale=en-US&&mtc=SHOPPING-BF-CDP-GGL-D25T-MULTI-NA-Multi-NA-SMART-NA-NA-NA-NA-NBR-NA-NA-NA-PortablePower_SmartShopping_HighOrganic&cm_mmc=SHOPPING-BF-CDP-GGL-D25T-MULTI-NA-Multi-NA-SMART-NA-NA-NA-NA-NBR-NA-NA-NA-PortablePower_SmartShopping_HighOrganic-71700000081625943-58700006942154417-92700062499001868&gbraid=0AAAAADq61UcTn6pCWXnwm7_gD2xgmJLE9&gbraid=0AAAAADq61UcTn6pCWXnwm7_gD2xgmJLE9&gclid=EAIaIQobChMIouHW_piA-QIVVMLCBB29kAGfEAQYAyABEgIO1fD_BwE&gclsrc=aw.ds#overlay) and it seems to be working just fine now, no smell!

Thanks everyone for the suggestions! My wife can finally be happy again!