This looks increasingly like a problem with Firefox 
Could you try opening the Javascript console (press F12 and click the Console tab), and type the following command and press enter:
indexedDB.open('wkof.file_cache')
Then click to expand the resulting IDBOpenDBRequest, and check if the error says ânullâ or something else:
https://sjc3.discourse-cdn.com/business5/uploads/wanikanicommunity/optimized/3X/f/e/fe07fc73789503a3d42d6faf6ffc4ad399640627_1_690x237.png
Thanks for the error info!
I did find the following info associated with that error:
For IndexedDB to work you need history turned on.
Options > âFireFox will Remember historyâ
As far as I can see itâs not documented anywhere but this is the triggerâŠ
Ah! Okay thank you so much!
Itâs back!!
Awesome! Iâll copy this solution to the Installing Wanikani Open Framework thread.
Just a feature suggestion I thought of.
Is there any way that we could get a display counter for the number of items that are at Apprentice 4? I always seem to find myself counting them ahead of time so I can plan for the number of lessons I do after I guru them.
Do you mean specifically Apprentice 4 of the current level? Or of any level?
And what about if you fail some of those reviews?
It almost sounds like you might want to try [SRS Grid Details]:
It will show you your current number of items at each SRS level.
If you use it, be sure to turn on the setting âBreakdown by sublevelâ.
I do have a script that gives me a level breakdown like that. I just meant something that would tell me how many Apprentice IV items I had in my current review queue, for any level.
Whether I miss some of them is irrelevant. 
I just figured, youâve already got a tab in the review popup that gives a general breakdown by overall level, appr, guru, mast, etc. But for Apprentice it might be nice to have it be a bit more granular.
Iâve upgraded to the new version of your script, and the count for my current column is consistently 2 above my actual review counts:
In this screen shot, my review count is 1, but Iâm hovering over the first bar and it says 3.
This is pretty persistent for me. After doing some reviews, the review count is always two higher than it should be. If I hit the refresh arrows, it still stays that way.
Can I help you debug this?
(Safari, OSX)
Now that Iâm looking for it, I havenât seen those two 䞻矩 reviews come up in a long time, but their pages say âavailable nowâ.
This might actually be a @viet problem, and is a server side inconsistency.
WaniKani / Vocabulary / æ„œć€©äž»çŸ© shows available now, but itâs not actually in my review queue, I havenât seen it a very long time (across multiple devices/browsers, including ones that have no scripts)
Make sure to update the Open Framework to the latest version. The new API still returns items that have been removed from WaniKani and @rfindley only recently updated the Open Framework to filter them out.
That was my first guess⊠and a good one.
In this case, though, those items are moved, not deleted. They moved from Level 21 to Level 23 on April 18th. And note that @chezmax is on Level 22.
I assumed that if they were unlocked already, the reviews would continue as normal, but that doesnât appear to be the case.
Today, Iâm putting together a tiny page on wkstats.com for people to submit their APIv2 keys to me for troubleshooting, so I donât have to post my email address every time I need an API key. Iâll post the URL when itâs done.
Anyway, I suspect this may indeed be an issue for viet and oldbonsai. I wonât know for sure until Iâve seen if thereâs anything in the API data that I can use to distinguish items like this.
I thought that was the case too⊠Maybe this is a bug on their side, unless this is intentional for some reason.
I was quite suprised because the timeline on my smartphone was updated and I could see some new options but the one on my computer didnât. I tried to disable all other scripts (keeping only framework and this one) but saw no changes.
In the end I decided to reinstall the script. When I clicked on the link I only saw the option to install but not reinstall.
I now have to timeline haha. Donât know why the old version 6.5.1 couldnât be updated.
By the way many thanks for this script which helps me a lot.
Ahh, itâs because theyâre named differently:
[
WaniKani Ultimate Timeline
Wanikani Ultimate Timeline
^
I tried to see if the name was different but didnât noticed this.
Well, now that Iâve figured out the case, itâs only slightly annoying 
At least itâll clear up in a little while when I hit level 23, assuming I ever do my lessons. 
This doesnât look like our issue.
It is not the case
Criteria for review is (in pseudoâish code) is user.current_level <= subject.level && assignment.available_at != null && assignment.available_at =< Time.now. It looks like the script is missing the level check?