I am currently working on a fiction book and my characters work for a company that in real life has been out of business for 30 years, but in my fiction book there is an alternate scenario and it happens to survive to the present day. This company is central to the book as many of the characters work there. Would there be any trademark or other infringment problem using the actual company name which has not been in business for 30 years?
Generally, it's a bad idea to use a real brand in fiction in any way, even if it's been defunct for decades. If anything in your work appears, to the holders of any trademarks related to the old brand, to in any way make them look bad, you could be sued -- and even if you win, you lose, because of the legal costs to defend such a case.
Besides that, some brands aren't as "gone" as we might have thought they were. To take one example, "Moxie" was a soft drink with a unique flavor that was common and popular decades ago, but it's not available any more -- unless you can find one of the dozen or so small grocery stores who still obtain and stock it across the USA. Someone still owns the brand, however, and writing anything about it is taking a risk.
If your characters need to work for a company that's defunct in our timeline, but not in theirs, make it something that never existed in our timeline -- not Studebaker, gone from the real USA since the 1960s, but perhaps Abernathy Motors (but don't do this without researching the name you select -- the number of companies that have come and gone over the past couple centuries boggles the mind).