my MAC computer no longer recognizes updates

Hello, island cheryl.

You didn't tell us what model and year your Mac is.

I suspect it's too old to upgrade further. It depends on the age of your Mac.

For details about your Mac model, click the Apple  icon at the top left of your screen and choose About This Mac.

These Mac models are compatible with macOS 10.13 High Sierra:

• MacBook (Late 2009 or newer)

• MacBook Pro (Mid 2010 or newer)

• MacBook Air (Late 2010 or newer)

• Mac mini (Mid 2010 or newer)

• iMac (Late 2009 or newer)

• Mac Pro (Mid 2010 or newer)

These Mac models are compatible with macOS 10.14 Mojave:

• MacBook (Early 2015 or newer)

• MacBook Air (Mid 2012 or newer)

• MacBook Pro (Mid 2012 or newer)

• Mac mini (Late 2012 or newer)

• iMac (Late 2012 or newer)

• iMac Pro (2017)

• Mac Pro (Late 2013; Mid 2010 and Mid 2012 models with a

   recommended Metal-capable graphics cards.

These Mac models are compatible with macOS 10.15 Catalina:

• MacBook (Early 2015 or newer)

• MacBook Air (Mid 2012 or newer)

• MacBook Pro (Mid 2012 or newer)

• Mac mini (Late 2012 or newer)

• iMac (Late 2012 or newer)

• iMac Pro (2017)

• Mac Pro (Late 2013 or newer)