Certainly pitch to the drain could be an issue, and have NO clue why you waited 8 months to resolve. If you are only noticing recently? More likely a water proofing/seep issue in the wall near where you can't dry the floor.

We've no idea the shower construction, the waterproofing used. Call back the contractor before the mold grows everywhere.

How long has it been since you last used that shower?

What takes forever to dry ? Do you mean just this spot or all the tile ? My guess if this spot only the slope not done right or there is water seeping behind the wall , both need attention and good luck getting the original contractor to do much but always worth a try.

The tiles in general take a while to dry since they are marble however, this spot in general stays wet by the wall. I am going to see if someone else can look at it first. The contractor will probably tell me its right. Do I need to contact a plumber?

You aren't going to get anyone to tell you what is wrong unless they simultaneously see an opportunity to GUT your shower!

You've let it go this long....why I have no idea.

You don't seem to know if the marble was sealed

You don't seem to know what waterproofing system was used.

You can continue letting water take its sweet time to dry, we'll hope it isn't a second floor bath that results in a nice ceiling leak below.

You can have a useless shower, or DO the DUE diligence that seems to have eluded you thus far, UNLESS that wet area started last week or even more recently.

Nobody here can advise. We weren't there for construction of the shower.

You really need to try to see if there is a source of the water other than just standing after the shower was used. Was this puddle noticed just a day or 2 after use? Or was it a week? a puddle will evaporate eventually, so if it is still there after more than a week, I'd be worried about a different source.

Inspect the seams between the walls and the shower floor. Now that you've dried the area, do you detect new moisture somewhere along the seam - especially closer to the plumbing?

Do you have an access door that opens to the pipes, on the wall behind the fixtures? Take a look in there for signs of moisture. Turn the shower on while you are looking, see if there are any drips. If you do find wetness in there, you do need a plumber.

If water isn't reaccumulating after you've dried it, then you will need to talk to your contractor about why there is this low spot.

@Jan Moyer I don't recall saying that I don't know the answers to those questions. I have another bathroom in the house which is why I haven't used the shower often. I noticed previously that the tile took long to dry but that is normal for real marble tile. I just noticed yesterday that there was water near the edge of the wall and floor. This site is to ask questions and get advise. Not to be "scolded".

Let me try this again, how long has it been between the time you used the shower, and you checked with paper towels? Can you ballpark it--Two hours, two days?

Sorry @Jake The Wonderdog. It was used Saturday morning around 9 am and it is still wet this morning (Monday).

What waterproofing system was used? Where are the pics of this during construction? Did you already look in the access panel behind the plumbing wall to see if there was a leak? Where are the pics of the shower as a whole, to show the location of the issue? A close up shows nothing. This is a garbage in, garbage out conversation. Unless you provide a heck of a lor more information than bad closeups, and answer all the questions that were asked, no once can even provide educated guesses about what is going on.