The bit that seems to get many people is you only switch on E2EE once, on the very first device. That device encrypts the data and syncs it again (this can take some time if you already have lots of notes). The other clients then sync and download the encrypted data. You do not need to activate E2EE on any other clients. One of the bits of data that comes down with the encrypted data is the Master Key. When this arrives the client will ask you to add the password for the Master Key. If you THEN go to the encryption settings you will see a field where you can type the password you used on the first device when E2EE was "triggered". You do not switch on E2EE in any other clients, you just add the Master Key password.
Does that make sense? I do not know if I have explained that clearly. I do have a step by step checklist I use for starting all over again that I could edit and share if you wish...