connecting two 12 volts batteries

Some things are simple for some and . ... Way too complex for others.

Batteries.. On of 'em Now I can look at an automotive type lead acid battery and tell you at a glance if it's a six or 12 volt and how to hook it up. Worked with both sixes and 12's since my teens (now lat 60s)

But ... One story here was how an RVer went to a dealer and had them put in new batteries.. WRONG.. Yup. A professional messed it up.. What more can I say.

LIkely a breaker tripped (Battery main) or the "oh-shi!!+_ fuse blue (Battery main) or the re-connect was done wrong.

here is a link to Winnebago Product resources. Manuals & Diagrams you can view / download info specific to your year & model.
Winnebago Product Resources

I got a call to help a friend with electrical trouble on his RV.

He had replaced his batteries and accidentally hooked them up in series. 24v....

We had propane to replace the converter, refrigerator control board and some light bulbs.

Parallel gives you 12 volts. ++ and --

Series will give you 24 volts. May have opened a fuse or some other damage. Some items are more tolerant than others.

Did the forum drop you here when you signed up? You probably wanted "Tech Issues" or "Class A" forums.

Connection of two 12 volt batteries in series sent 24 volts through your system. IMO you should start by checking all your fuses and breakers. Pray first.

They should be in parallel.

Something probably got blowed up when you connected 24 volts.

I’d check the fuseable links, breakers, fuses.

Insurance may cover it.