SONOFF 4CHR3 with eWelink - How to connect a 433 MHz radio remote control?

I have a Sonoff 4CHR3 connected to eWeLink, everything works fine. My question is this - is it possible to connect a radio remote control to this so that I can control the channels from the eWeLink software as well as from the 433 MHz radio remote? Is there any additional software or anything needed for this? I searched on the internet that you can by quickly - double pressing any button on the Sonoff and the corresponding button on the remote. I tried before adding it to the eWeLink to train the remote itself and it didn't work. It simply switched on and off a particular channel on the Sonoff and nothing paired. I did the same on one new one not connected to the eWeLink and with the other connected. Please help!

Which remote control?

Instructions from the internet:

Quote:

Sonoff 4CH PRO R3 adding 433 MHz radio remotes
Each of the Sonoff 4CH Pro R3 relays/channels can also be controlled by a 433 MHz fixed-code remote control. It is possible to add a maximum of 4 remotes to a single channel.

Adding remote controls:

Press the button corresponding to the relay you wish to control with the remote control, e.g. R1, until (approximately 3 s) the blue Wi-Fi LED flashes red once, release the button and press the button on the remote control.

Deleting remotes:

Press the button corresponding to the remote control you want to control, e.g. R1, until (approximately 5 s) until the blue Wi-Fi LED flashes red twice, confirming that the remote controls have been removed from the device.

.

Picture of supported remotes from the internet:
.

I purchased 2x Sonoff 4CHR3's from eWelink for around £79, on top of this I bought one Sonoff 4CHR3 from Supla on Alledrogo for £137. I have these connected and added to all these 12 channels of lights, tubes etc. Everything works fine, whether on the eWelink or the Supla.

I bought 2 remotes to try it out and the arsehole.

As recommended by mr.kaczmarek2, none of the Sonofs, when pressed for 3 seconds, responds but switches the channel in question (ON/OFF). Whether it's the first, second, third or fourth (I hold for 3 seconds), the indicator light doesn't blink red or flash. All that happens is it puts the channel ON or OFF. I have tried and for 5 sec. NOTHING happens, it just turns on or off. What am I doing wrong???

Added after 3 [minutes]: .

Remote control good or not, I don't think it matters, since the wi-fi LED on either Sonoff doesn't respond anyway. But I'm adding a link to the remote control, which is what I purchased:

https://allegro.pl/oferta/pilot-radiowy-4-prz...dla-sonoff-moes-rf-433mhz-ev-1527-15214226498

HELP!!!

I would start perhaps with the basics, are the Sonoffs you have 100% with RF or can you look inside? Maybe someone made a mistake and gave a version without RF.... Is there a battery in the remote control? The offer in the link says they sell without.