So, my account is pretty much back in order. I wanted to update those who've been so helpful in this thread, as well as record for the future benefit of other users, how things panned out. After some frustration in chasing Support for responses I was finally in touch with a senior support rep who was good at replying promptly and even logging in to help me after his own shift had finished. Thanks, Karl G. In the end Evernote could not restore my data from their end and so worked with me to restore my data from my own Time Machine backup (not yet got it set up? It's well worth having TM up and running, folks!) These are pretty much the steps I followed to restore my account: 1) Move the old database from its location on your Mac. To do this: Close EvernoteYour database is in a hidden directory. You can access it by opening the Finder, then selecting "Go" from the top menu and hitting the "Option" key. Once you have done that, you'll see the "Library" folder pop up. Select it. Next, I'm going to have you move the "your username" directory to another place. (Note: You may not have a directory in both places. Please remove whichever ones you do have, and make sure that you no longer have either before moving forward. If you are directed to "merge/replace/keep", choose to "Keep a Copy".):First go to:~/Library/Containers/com.evernote.Evernote/Data/Library/Application Support/Evernote/accounts/Evernote/<yourusername> and move the "your username" directory to another place (like the desktop). If you are directed to "merge/replace/keep", choose to "Keep a Copy". Then go to:~Library/Application Support/Evernote/accounts/Evernote/<your username> and move the "your username" directory to another place (like the desktop). If you are directed to "merge/replace/keep", choose to "Keep a Copy". 2) Once you've moved the database, you will want to access Time Machine's backup and place it where your database was previously stored: go to the location where your Evernote database was stored, open Time Machine and locate your username folder in the same location from Time Machine's cache and restore it from the backup. You can now insert the directory you restored into the location where your database from Step 1 was found (Note: the folder will need to be named with your username or Evernote will not recognize it): IMPORTANT: Take the Mac off the network (Turn off Wireless/Airport)Open Evernote (if it is not currently open)Sign out of all of your Evernote accounts (if you only have one account, just sign out of that account)You should now be on the Sign-in pageUse the hotkey combination: CTRL + ALT + CMD + E (this will export your entire account to a folder which will preserve your individual notebook structure as individual .enex files, however, it will not preserve notebook stacks)After doing that, connect to the network (Turn on Wireless/Airport)Click the "Sync" button (your old notes will be over-written by the server notes)Once all your notes have been pulled down from the server, import each of the .enex file(s) INDIVIDUALLY back into the Mac client (File > Import)Sync your account once notebooks have been reimported Two comments and one remaining issue:In the final step I synced my account after importing each notebook, just to ensure that sync happened properly and to avoid Evernote having to cope with a single mega-sync after importing all of my notebooks. This meant that this stage was quite time intensive as I had to individually import and sync each of 65 notebooks. As noted above, notebook stacks (as well as tag hierarchies) are not preserved by this process and so had to rebuilt; that didn't take too long though. In order to get all of my data synced back up I had to have my account allowance boosted by an extra 5GB. Karl did this in advance and so all was fine. But it was something that the very first support guy failed to consider.A remaining issue: Karl had thought that whilst this process would likely break note links between different notebooks, it would preserve those between notes in the same notebook. This issue was discussed above in this thread, but I was happy to go with Karl's view. Sadly, as predicted in this thread, all note links were broken by this process. Karl later realised this and apologised: "Unfortunately, there is no way around the lost note links issue since syncing up to the server is creating new note ID numbers (GUID's) and thereby breaks the note links. Apologies for the misinformation. I remember testing this now and not getting the note links back so I'm really not sure why I wrote that the note links would work." So, I'll need to rebuild note links as and when I come across them. This whole situation and resolution has highlighted for me:I should be less liberal with note links and less reliant upon them if they are so easily lost. I should be slow to act on (major) instructions from support and should take time to think through (or ask on here about) the implications. (for those who've not read this whole thread, I got myself into this whole mess by following what seemed like straightforward instructions from Support, for fixing a syncing problem, but instructions which omitted to mention some serious side-effects and failed to consider that I would need an increased data allowance in order to follow them through.