why cant i get the ios15 on my 6s plus

hjklm wrote:

i have the old 6s plus and I cant get the ios15 upgrade and therefore I can't get ESPN app anymore. Any tips?

Look here for I can't If your iPhone, iPad or iPod touch won’t update - Apple Support

You have a 6 Plus - which cannot be updated further than iOS 12.5.5

can someone please advise how to update ios later for 6s PLUS. currently 12.5.5

A device running iOS 12.5.5 can not be an iPhone 6S Plus. Instead it has to be an iPhone 5S, 6 or 6 Plus. Neither can be updated further.