Hello, and welcome to the forum. Sad to hear you're having difficulties.
Yes, that's how it should work.
Step 5 says this:
Once this first synchronisation operation is done, open the next device you are synchronising with. Click "Synchronise" and wait for the sync operation to complete. The device will receive the master key, and you will need to provide the password for it. At this point E2EE will be automatically enabled on this device. Once done, click Synchronise again and wait for it to complete.
It doesn't mention enabling it on subsequent devices, because you needn't do that.
I think what you should do is: enable it on the first device. Add a note, for example.
Then, according to step 5, set up your phone to use the same synchronization target (OneDrive in your case). Start synchronization and wait.
You should see '
Encrypted' notes start popping up (if you have any notes, that is.)
Then just wait.
Eventually, one of the resources Joplin dowloads from your folder will be the master key, encrypted with your password.
Once this happens, Joplin should prompt you for this password, you will just enter it (the same one you entered on your PC where you first set encryption up) and wait.
From then on, Joplin will use this master key to decrypt and encrypt all your passwords. No need to have multiple.
Hope this helps.