[Customer Service Response Time]

Lately it seems like they respond much faster, within a day. I'd suggest be patient wait another day or so then send a follow up message.  They may just be experiencing high demand. 

[Cash Advance question]

Yes the same happened to me, seems to come and go. Based on what I've seen it's indeed down to your overall positive metrics/eligibility criteria (possibly including net income and projected income). Just keep delivering great work with your orders and it'll come back available 🙂

[How do I rank a Fiverr Gig?]

In addition to the great answer above, use the buyer request section and social media/sharing gig to send special offers to get an additional spike in orders. Then deliver the best possible work you can, resulting in consistent 5 star reviews which will improve your rank.