Breaker issues

Good evening I am new to this I have a 1999 35 ft newmar Dutch star with a Ford Triton V8 have twin AC roof mount and my problem is I purchased a standalone portable air conditioner that pulls only 10 amps according to the label and as a regular three prong plug-in and every time I plug it in to the motorhome when I am on shore power now that is I have only access right now to a regular outlet in my carport regular 110 and when I plug the portable AC into the motorhome anywhere in it it then throws the breaker in my panel now I have 2 50amp main breakers and three sets of 20 amp 15 amp breakers besides that. I have made sure nothing else is running it's a 12,000 BTU portable AC and like I said it says it only pulls 10 amps if I plug it directly into the house and not into a socket in the RV then it will run fine I'm wondering if I possibly have two smaller cord running from the house to the motorhome but besides that I plugged my motorhome into itself fired up the generator which is an Onan 5500 and put one of the rooftop ACs on and as soon as I plugged in and turned on the portable AC it killed the generator which doesn't make any sense just looking for some help I'm going to talk to an electrician friend if I can tomorrow anybody have any ideas thank you and it much in advance for help