No blockage.

The plumber can remove the trap under the kitchen sink or laundry tub and run a small snake through the pipe until he either clears the blockage, or hits it and can't get through.

I had to replace the entire cast iron sewer pipe system because of in-line blockages.

Or is it the main fireplace chimney that has a crack or blockage, and the fireplace has a gas line?

He spent about 15 minutes with it and the wipes were never ending so he informed the tenant that per their lease any tenant caused blockage is their responsibility so they would need to call a plumber (we always do the first one for free because it could have been from a preexisting issue).

Likely a blockage in the sewer line.

1) Small Animals, skunks have been persistent this year.2) Plumbing blockage due to tenant, I clearly indicate that's not in my scope of work.

This crimping of the line causes blockage issues with leaves etc. so you may want to look at the angles and connections.Also if the gutters are not attached properly the water can run behind instead of draining down.

For example, my lease says (in part): "Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines."

There was a blockage in the hose and it caused substantial damage.