The thing that strikes my eye the most is that your gig’s URL doesn’t match the gig, URL and gig are for 2 different things.
Maybe try creating a new proofreading gig with a relevant URL and see how that goes.
According to posts by many people, the search algorithm favours the URL above the tags and people who are searching for index/glossary creation might not be looking for proofreading.
Also, you’re not supposed to change gigs in a substantial way because else you may have reviews on a gig for X that you got for doing Y, hence it’s not possible to change a gig’s URL. If you want to “give up” a gig, don’t repurpose it, pause it and create a new one for the new service you have in mind. Editing is for things like changing the description, the pricing, etc., but not to change ‘what the gig is about’. That might be an issue too.
The description in your premium package seems a bit confusing: “Idealistic for writers who need help writing.” Did you actually mean “Idealistic” here or was it a typo and you meant “Ideal”? A typo in a proofreading gig obviously could be a big issue.
“that call themselves authors” I’d definitely change that.
““I do not work nights, weekends or any holidays. Please be respectful of that and order EARLY.””
I’d change that too, apart from it not sounding very welcoming, how you schedule and structure isn’t really anything that concerns your clients beyond that you’ll deliver on time.
It’s confusing IMO, what does it even mean, ‘I’m not supposed to order Thursdays or Fridays because then you’d have to work the weekends?’
Your delivery times should be so that it doesn’t matter when a customer orders, they want to order when they are ready to order, not wonder about which time it is for you right now, whether they may only order on Monday morning your timezone because that’s the only way you’d be able to do their amount of words without a weekend in-between and … 'well, of course I don’t expect you to work at nights but what does that mean for me, I have 50K words, I see a gig for 50K words with 1 week delivery time now may I order that now or not because you didn’t figure nights and weekends in and … how am I supposed to know if you’re on holiday now? (That’s what out of office mode is for, after all, if you’re on holidays you should use that or pause your gigs if you don’t want orders during that.) … I hope you see what I mean, it’s not a buyer’s responsibility to figure out when they should ideally order but you should set up your gig delivery time/words in a way that you can deliver on time, never mind when the customer order (as long as they don’t send more words than they bought with your gig, of course).
Just some ideas, hope it helps, but, as always, the ways of Fiverr’s algorithms are mysterious, it could be none or either or all of the above, or what humanissocial already said, or something else altogether - like, make sure your gig even is showing up in search at all, especially in case you edited it as you said you recently did.
There also could be more competition now with gigs that attract your former clientele more than yours, etc.
Have a look at where in search your gig shows up and what and how others in your niche who show up on the first one or two pages are doing.