Need help diagnosing server connection isssues

I could use some help figuring out what's going wrong. I'm hosting an Ark server (via Ark Server Manaager) and it is starting up and running fine (and one of my friends can connect), but I'm having trouble connecting myself. I was able to get on once, but that seems like it was more of a fluke than anything and I haven't been able to replicate it.

The server is hosted on a fairly fresh Win10 install with ports 25810-25830 and 27015-27025 forwarded to the machine through the router (to leave room for the eventual cluster I want to create). The current server is running Aberration on server port 25810 and query port 27015 and it has Crossplay turned on (since some potential players have the EGS version). I can provide other details if-needed, but that seemed like most of the likely relevant info.

I'm trying to connect to the game from my Steam install of Ark and I'm having little luck getting on the server. I've added the server to my Steam server list (by adding the external IP, which it recognized the server name/map/etc from), and it shows up as a favorite in the in-game server list, but I can't successfully connect to it.

When loading from directly opening ShooterGame.exe, the server will show up in the server list as a favorite. Clicking on it to load will start attempting to load PrimalGameData_BP a few times before bouncing back to the server list and giving a Connection Timeout message after a minute. If the game is launched through Steam instead, the same procedure often goes straight to pausing and then giving the Connection Timeout without visibly attempting to load at all, but that varies slightly. Either way, it's timing out instead of loading in properly. And subsequent attempts to load in always just stay at the server list screen saying "Joining server" until they time out.

Another thing I've attempted is adding +connect [IP]:[port] in the Steam launch options (and in the options for launching ShooterGame.exe manually). That gives an Attempting to join a game from invite or direct join... for a minute and then pops up a Lost/timedout connection to host error. Alternatively, it'll also sometimes give a more immediate Unable to query server info for invite error instead.

Another thing I've tried is loading into a single player map and then connecting via open [IP]:[port]. This has had the most mixed success. The vast majority of the time, it waits for a bit and gives the Lost/timedout connection to host message. However, one time it did start trying to load in and then failed when trying to load Snapshot_16 (I believe); that also seemed to cause some kind of server hang/DC, since my friend got kicked from the server when that happened and I ended up restarting the server. Another time, I was able to load in perfectly through that method and played for a few hours; but it hasn't worked since then and I can't seem to recreate it.

So far, I've tried running netsh winsock reset on the machine, a nubmer of Steam file verifications, a full re-install of the game, and countless repeated attempts to connect. None of those seems to have had any effect on the issue at all.

At this point, I'm wondering what I'm doing wrong. It seems like it must be some kind of stupid/simple issue, but at this point I'm running low on ideas and I'm hoping someone else has an answer as to what the issue is. Does anyone have any clue/ideas what might fix the problem?

#Update/solution: Disabling "NAT Acceleration" in my router's settings (and it was buried pretty deep in the settings) fixed everything.