After cleaning the sewer line my toilet on my second floor still does not flush. What do I need to do?
First I thought it was the sewerline that is clogged but after cleaning it and installing the toilet back in, it still flushes slowly or won’t flush at all. I checked the water compartment and everything seems to be working fine. I wonder what else do I need to check or fix? This is one of the 3 toilets on my second floor and the other two are working fine.

Try cleaning out this same line, but go in through the vent pipe up on the roof.
You have a sewer line blockage somewhere in the interior walls of your house, unless if you have two underground sewer connections coming from under the house from a later added on room addition. You can rent a electric roto-rooter from a rental shop to snake out the lines, or call a plumber. A snake out is running the coiled wire with a hook on the end to attach to the blockage from the roto-rooter
did you check the trap in the toilet when you had it off ?
sounds like there’s something in the toilet trap
get a toilet auger ,[at a hardware ] run it thur the toilet
I agree with Don, it sounds like your vent is clogged. Here is the scenario, when the water does go into the pipe it needs to be able to displace and replace air as it moves, if the vent end of your pipe is clogged this can not happen. When you removed your toilet to clean the drain pipe did you try pouring water down it say from a five gallon bucket to see if the drain worked? If it did not work, it’s your vent or still something in your drain, if it did work it’s your toilet. You should be able to head into your attic and find the vent stack for that particular toilet, you can try drilling a small hole in the vent stack in various places to see if you have a clog in the vent stack, you will hear air sucking through the small hole when the toilet is flushed assuming that you drilled the hole pre to the clog in the vent, I have pulled a dead bird or 2 from a vent stack that has caused this precise problem.