There are 3 reasons I can think of that sellers and their listing agent won’t like your pre approval letter.
The difference between a pre approval and pre qualification has to do with the amount of information the lender has taken from you to give you the letter. A pre qualification is very basic. It states that on the surface you look like a good candidate for a loan. A pre approval requires more documentation from the borrower to support the letter.
I know you want to use the lender that you have been doing business with for years from your home town. The problem is that the seller has never heard of them. Each state has different rules and regulations for approving mortgages. Using an out of state mortgage company can cause unnecessary delays. You should always, ultimately, choose the one you want but know the potential complications it can cause.
There are a couple of mortgage companies out there that are notorious for being difficult to deal with. We do this all the time and have learned from experience to avoid these lenders when possible.
Your buyers agent should have a list of preferred providers.