Hi I have a Mac 10.8.5 and I can’t install Microsoft 365

Consider the open-source productivity suite LibreOffice:

https://www.libreoffice.org/discover/libreoffice/

You will need to update your OS to at least 10.10 Yosemite, but it will work and reads/writes MS Office files. You might as well update to your maximum:10.13 High Sierra. We have a 2011 iMac running 10.13 that shipped with 10.8. Ours runs as well or better than when shipped on OS10.13.

For macOS software downloads see:

How to get old versions of macOS - Apple Support

Use Safari for downloads. Firefox is note working properly for mac system downloads at the moment.

Hi Keza1676***,

10.8 simply won't work with 365. In fact, you Mac is just too old for 365. You need at least Mojave 10.14. You Mac only goes to 10.13 High Sierra.

Cheers,

Jack