if anyone lands here looking for the same solution…
I wasn’t syncing on Android, I was trying to sync from the iPhone / MacOS to a Windows computer… weirdly, when I copied the code from iPhone/MacOS and pasted the code on Windows, the word counter was saying 23 words and I was getting the “Invalid sync code” error message… I tried a few times and had no luck…
eventually I just typed the whole code myself (the 25 words) and then it counted 25 words and the sync worked…
I thought that there must have been something missing from the copy / paste process but when comparing both strings, they were identical…
I copied the code from MacOS into Notepad++ to try to get rid of any formatting etc, but had no luck still, so I reckon the Copy / Paste process between the 2 operating systems must be copying some blank characters or something.
To add, I copied the code on Mac / iPhone… then pasted it on a Whatsapp message to my partner, then went on the other the Windows computer and copied from Whatsapp to Notepad++ and from Notepad to Brave…