I was just rejected for a personal loan from Best Egg, and the top two reasons on the letter are written exactly as:
Insufficient credit established Insufficient history of activity on open revolving accounts
I understand the last one bc I opened three new credit accounts in the last year and two others the year before that, and possibly also bc my oldest revolving is a card I don't use. But what do they mean by the "Insufficient credit established" part? They checked Experian (returned a 726 btw) and on Experian's own credit tracker that I pay for, they score my credit "mix" as Exceptional, which is the highest category.
Instead of mix, does "insufficient credit established" refer to a dollar amount? Or overall age of my credit? That would be weird bc according to Experian again:
They have to pick from about 80 different standard terms when defining the reason for denial, and it's not uncommon for the best available term to not clearly explain the reason.
In reading between the lines a bit I think they're trying to tell you that while you have a long term history they don't like that it is thinly populated with open accounts more than 2 years old. Just winging it a bit I am guessing that you have the 22yo account and maybe 1 other old one, possibly with 1 of those 2 closed less than 10 years ago. This may not be quite correct in your case, but it would be consistent with both reasons given.