[Why a big jump in impressions on the first day?]

With a good title and SEO-optimized description, you will get rank and reach more people on your profile. Fiverr gives a chance to new sellers for ranking. After it totally depends on your service, gig picture, and prices for conversion. 

[impression problem]

First, try to find low-competition keywords. Make a good SEO-optimized title and description and set a reasonable price. 

[Fiverr gigs disappear and didn't find on any page.]

I hope all users doing well. 
As you read my topic title of Fiverr gigs disappeared and didn't find on any page. I will describe this issue in detail. I faced this issue two times. The first time I faced an issue about a de-rank account all gigs were de-rank even though I checked all of the Fiverr pages for specific gig categories. 
 

How gigs are ranked after de-rank?

This is a very tricky question and has many factors to involve in ranking gigs. First of all, we need to know why de-rank accounts or gigs. There are some possibilities of de-rank accounts and gigs with bad ratings, canceled orders, and reports from buyers. 

Note: My account is on level 2 and also completed the requirements for top level. I also used Fiverr promotion.

Personal Experience after de-rank account:
Luckily there were some regular clients and I got many good ratings and positive feedback from my old regular buyers. I also updated my gig with good SEO and everything which possible I did it but nothing happened. After that, I continued online on Fiverr and got more good feedback from my regular buyers.  They make a good effect on my de-rank account but it takes a minimum of 6 months to rank again on Fiverr. I was very happy to get back Fiverr promotion and appearance gigs on 1st and 2nd pages. 

But after only 7 days account was again de-rank and all gigs disappeared from the search result. It doesn't appear on any page of the specific category. Even I get many positive feedbacks and ratings and didn't get any bad feedback or ratings or anything from these seven days. 

Why this happened?

I don't know why this happened again. I hope Fiverr gives a better answer to this issue. 
I also attached screenshot one of my gig impress result.