Ares75 - be warned, it may not be marble your artisans are waiting for. The update on what's needed doesn't always change very quickly. The best thing to do is make sure you have your wood & sculpture ready & close by as well. If this doesn't work & your employment is fine, the only other thing I can suggest is to check you're not stockpiling any of the building materials by mistake ... it's very easily done

If it's none of these, post again & we'll have another go

I believe each storehouse only sends one load to one artisan at a time. If you more storehouses with marble in each, you should get marble moved faster. Remember that if you have any storehouses with marble that are a long way from the sanctuary, they still might be picked to send a load to the sanctuary and this will slow things down.