Faustus will very often say that I do not have items to sell.

Whether it is scarabs, or tattoos, or anything, he will very often tell me that I do not have any of those items to sell.

Is this a common problem for others? Is there a fix? Some sort of reload to make him see my stash?

I don't know if it's a bug or not but from my experience Faustus can't see scarabs not in inventory ( such as a stash tab).

So the workaround for me has been to put non currency items in inventory.

I say non currency in the sense of items that cannot be stored in the currency only stash tab.

Faustus "owned" tab is instance specific for items in your specific stash tab. If you spawn into an instance, he will show you own no essences, for example. Then you walk over to your stash tab, open essence tab, then check Faustus owned tab again and everything should populate accordingly. Load into a new instance and the owned tab will default back to like you never opened the essence tab. It's annoying at times, but before the new ctrl click feature, I would intentionally reset my instances so I could hide tabs I had opened to avoid scrolling past stuff I didn't want to list.

Personally, I'm not a fan of all of the scrolling so I just load my inventory with like 15-20 different types of scarabs, fossils, etc and just price check them using the Ctrl click direct from inventory to "I Have". Has made Exchange selling far better for me.. gold tax aside (have used 500k+ in exchange tax for longer selling sessions).