Is it acceptable currently to ask for a cancellation fee due to no fault of the Notary but because of illegal or questionable circumstance that prevents the signing ceremony to take place? And what would be reasonable? 50%?
It depends on your state. Some states, like mine, don’t regulate notary fees at all. Most of the rest allow a travel fee. So you could charge the travel fee even if the notarization can’t be carried out. If your state regulates fees, and the signer comes to you, I doubt it would be proper to charge a fee.
Personally, if the signer came to me (rare) and I couldn’t notarize, I wouldn’t charge a fee.