I have just received alternative instructions from the manufacturer on how to connect the remote control.
Thanks to Digitec support! .......PAC EL112- PAIRING PROCEDURE
1- Standby Mode
2- Make sure that the LED of the CST RCU flashes red immediately after inserting the batteries
followed by a white line
3- Press and hold the Mode button on the remote control for about 10 seconds until a dot appears on the display.
appears on the display, then you can remove your finger
4- Press the arrow button on the air conditioner until a dot appears on the display, then withdraw your finger.
then withdraw your finger.
5- Please note that a rapid white light should flash at the end on the remote control
which means that the pairing is working!

Note: You have to hold the arrow button for a really long time until a small square starts to light up! and only then did I press the mode button for 10 seconds! If you have any questions, please write here.

The pairing instructions from DeLonghi are incorrect. Do not press the MODE button on the PAC, but the up arrow button! On the CST, remove the batteries beforehand, wait briefly and reinsert them. Then press and hold MODE until the white LED lights up briefly twice. Then press and hold ⬆️ on the PAC until the small square between the standby lines flashes. The pairing process then starts.

I have the same problem. The remote control also lights up every 20 seconds. However, the remote control has a red dot in the app and it says: not found. No possibility to connect. I receive a new remote control directly from the manufacturer (otherwise I would have had to send the whole device back). About 5 weeks delivery time. The remote control seems to be a problem.

I'm currently experiencing the same problem. I've opened a warranty case and I'm sending the whole device back for "repair". I hope it will work afterwards. I recommend that you do the same.

Same problem for me. Answer from support (works now too):
Try again with a repeat pairing.
REPEATING THE COUPLING OF THE CST REMOTE CONTROL The CST remote control is already paired with the Pinguino device. If the user wants to pair it with another Pinguino device or when pairing a new CST remote control, he must put the device in standby mode and press and hold the MODE selection button (D6) on the CST remote control for 10 seconds. The LED (D10) will start to flash periodically to indicate the pairing phase. The user is then prompted to press the button (C4) on the Pinguino for 10 seconds until a double beep sounds. The pairing phase is indicated on the display by a rapidly flashing dot between the digits. When the two devices have completed the pairing dialogue, a double "beep" sounds and the normal standby display appears on the screen. Pairing must be completed within 60 seconds.

Same problem here, also cannot be reconnected

I had exactly the same problem and also tried unsuccessfully to reconnect the remote control. Then gave up at some point. I'm curious to see if it works for you.

That probably won't really help you either: but in my case, the remote control was already connected, as the instructions say, and I didn't have to do anything else.

That probably won't really help you either: but in my case it was the remote control,