I had to go through a few extra steps but my Tiddlyspot wikis (all 2 of them) upgraded.
I'm on Windows 7 with Chrome Version 54.0.2840.71 m.
I didn't follow the proper process. I did the following:
1) opened my tiddlyspot site and used the browser save page to save a local copy.
3) drag-and-drop the local saved copy
4) the save button on the upgraded tiddlywiki prompted for a local save
5) opened the locally saved upgraded file
6) added back my tiddlywiki credentials and used the in-wiki save button (it saved to tiddlyspot)
7) Opened the upgraded wiki from tiddlywiki in a new tab (at this point I have 3 tabs with the wiki in it (old, local upgraded, new)
8) Confirmed the upgraded wiki seams to work right, re-save it and make sure it said it worked.
9) close the other tabs.