Inspiron 15 beeps and cannot get support because service tag number and express service code not recognized

I have had my Inspiron 15 3000 series since the end of August and was liking it until is started beeping a few weeks ago - sounds like a truck backing up.  It does it 5 times and repeats 3 times when starting up.    I tried online support but you cannot get anywhere until you enter your service tag number or express service code neither are recognized.  I tried calling support but they could not identify my computer with the numbers either (I took pictures of them on my tablet and made them larger so I know they are right).   I purchased my laptop on line. Initially there was a message about the power source, but I have popped my battery out and  back in and the error message no longer pops up but is still beeps.   I am at a complete loss as to what to do at this point and am incredibly frustrated.