@Vladek 

I am not expert for this problem bat I assume problem is maybe in modem bin file. If modem (Huawei E3131s-2 is 3g only modem, network types: 2g only, 3g only, 4g grayed and Auto) send to router that there is 3g and 4g network in range, router decides logicaly what to do. I am not clear how 3g modem can detect 4g network, but if he can detect then modem bin file from TP-Link probably sent this information to router. So when 3g signal is "stronger", then router choose 3g. By the way, why modem bin file for my modem has 4 files, Huawei T-mobile #1,#2,#3,#4? Why modem bin file simply does not block 4g signal: It should know that modem is 3g (and 2g) only.

If I am completely wrong about modem bin file, why router setup has no option what network to choose, but offer 4 operations modes which is more challenging. Maybe It should be fixed in next firmware version. It would be nice.

I tried with profile, firmware is the newest, nothing better, and I still looking for better 3g (lower 4g) signal in my house, mesured 12 meters from modem and ruter to place where i can find and connect to 3g network.

At the end, I use mr3420 with E3131 for internet and wireless only.

Thanks for replays.

@Vladek 

Dear Kevin,

today I red your post in my gmail. As I said: my Huawei E3131s-2 is 3g modem. Sim card is 4g capable, confirmed from ISP.

In my E3131 3g modem connections settings are: 2g only, 3g only, 4g grayed (unreachable), and Auto.

With previous ISP I had the same Huawei E3131s-2 stick, and obviously sim card was only 3g capable, because connections settings were: 2g only, 3g only and Auto.

That means I have 3g modem with 4g sim card and everything work fine with internet managers and direct connection from Win 7 64 bit (without internet manager).

So sim card knows that modem is not 4g capable (4g grayed). Why router does not know this?

I opened tp-link page you sugested  .... /en/support/faq/1663, but  mr3420 has not the same settings options as Archer mr200. I have no any option to change network mode to 3g only and 4g only as tip #2 says.

@Vladek 

Dear friends, I finaly  succeed and now i can connect to internet.

I created my profile and set dial number and apn. Technicians from my ISP told me that apn is: internet (just one word).

No connection. Then I found on some Croatian forum that apn for another Croatian ISP is: internet. name of ISP.hr

I tried with my apn: internet.my ISP.hr and connected without problem.

My procedure is:

turn on router

wait until On led and Wifi led stop blinking

plug in my usb modem to router

after a ten/fifteen seconds Internet led appear orange and after second or two is green

I am connected to internet. Connection type is 3g.

If I reboot or turn on router with modem already plugged in, there is no internet because Connection type is 4g.

I assume that it is not normal. Anyway I am satisfied. with my procedure.

Many thans for your efforts which help me a lot.

Good day.