pamntrev: I applied to increase my loan to buy a new car, over 5 years the same as the last one, payment are almost the same
Are you saying you applied for a new 5 year loan while still paying the last year of the previous loan, or are you saying part of the deal was to pay the previous loan off early?
If the former, then while the new loan payments may well be "almost the same", for a year you would have double payments to make. That might have failed the application on "affordability" grounds and nothing to do with "credit rating".
Even though you were told that, often that's a staff competency issue who just tell you what the automated process says on their screen without actually understanding why.
Lenders usually don't give a proper explanation, however one thing you are entitled to be told is which credit reference agency was searched. You have checked your score on Credit Expert (Experian), but maybe you also need to check your credit report on Equifax.