[Batje]

Batje, your advices are not grounded at all. NAT or not NAT does not matter as long as you connect both ICOM and computer to LAN and not external connection. Reserving via iToolRadar over wireless connection works without any problems. And for coding with ESys wireless connection is ok as long as you are not flashing. I never turn off antivirus and firewall on my computer too, just configure firewall to always allow istagui.exe and istaoperation.exe. Never ever had any issues.

P.S. I use windows defender as antivirus and standard windows firewall.

Well in theory it doesn't have anything to do with internal networking, on that perspective you're right. but i have worked for a company who installed IP camera's and i have spent hours on reconfiguring clients network setups to make those camera's accessible on both the LAN and WAN.
I had a customer once where i had spent an entire day figuring out why i could not access their camera even on the LAN.
On that particular router i had to turn off NAT et voila, it suddenly worked on the LAN side.
It confused the sh*t out of me, cause NAT should only translate between internal and external networks however it seemed that on some routers there where other functions tied to the NAT as well.
That's why i made that statement.

I know when reading this it makes no sense but what do you have to lose when you want to turn a router into a dumb access point?

For the record, my ICOM works flawless on wireless connected to a Ubiquiti Unifi AP. i was only suggesting that to rule out other causes (like my mystery with that one client) because for connecting wirelessly to an icom you shouldn't need anything more than a plain old access point.

[Node]

Well, TP-Link router was specified and in my experience they work ok.