What sites have you tried? Do you have a link to one of your listings?
Presentation (quality of pictures and text), price, and other factors may affect ad response in addition to listing site(s). Need more information to provide helpful guidance.
You may find some of the suggestions in this recent thread helpful.
https://www.classbforum.com/forums/f...-rv-13070.html
I track ads on RVTrader.com for units similar to mine (just to keep up with the market). I've noticed an increase in the number of units for sale and a softening of prices recently. It appears the diminishing severity of the pandemic along with the rise in gas prices is cooling down the overheated RV market. You can expect yours to take longer to sell.