I have been running a server for a few weeks now with some friends. It started out as vanilla but then I migrated over to a forge server. The friend who is having troubles  connected and played just fine when it was vanilla server, but then took a bit of a break. Now that my friend is trying to connect again, we quadruple checked they had the correct mods installed, and the correct version of Forge client, but every time they try to connect to the server, it won't let them connect. The 25565 port is forwarded properly, and as mentioned, no one else has issues connecting. My friend can connect to other servers as well. I will refer to my friend as "A" (They want to remain anonymous, I have also censored A's IP address and username/UUID in the logs). My server is hosted on a dedicated machine running windows 10. A can connect to another vanilla server I have running on the same machine that is 1.14.4 and can connect to the Forge server after I ran an exact copy of it as a vanilla server (didn't use the .bat file to run the forge .jar and instead just launched the 1.14.3 minecraft server jar). Sometime after converting the server to a modded Forge server it regenerated the world and got a new seed, I didn't realize until I loaded some new chunks and saw strange chunk borders. Once I realized what had happened, I used NBT editor to change the seed back and never had a problem since. I don't know if that is relevant but I figured I'd include everything.

Troubleshooting steps and information gathered so far:

-Resetting A's Router/Modem

-Reatarting A's Computer
-Quadruple checking the mod list is correct and up to date
-Making sure A is running the proper client version of Forge
-Restarting my server

-Uninstalling and reinstalling Minecraft client on A's computer

-Uninstalling and reinstalling Forge client on A's computer

-Starting the server with online mode false

-Temporarily deleting A's player data and achievements .dat and .json files respectively

-Changing the server port to the 25555 port that was confirmed working on the vanilla 1.14.4 server

 

Logs:
https://pastebin.com/6u5XDaeZ
Everytime A tries to connect, lines 94 and 95 appear in server logs. To be clear, I started the server, had A attempt to connect, and then turned the server off to grab these logs, that is why they are sparse and include startup etc.

Screenshot of Server mod folder:

 

Screenshot of Client mod folder:

 

They are mismatching between client and server because Appleskin and Enchantment descriptions are client only, and Morpheus and Fast Leaf Decay are server only.

Edit: This is the message A see's whenever trying to connect and failing, it says "Encrypting..." and then gives this:

Edited July 31, 20196 yr by Pohds

my problem is quite the same, there is standing: connection lost: Disconected

Pohds did you fix it?