Most popups/error messages say "UNDEFINED"

It’s a two step process to get from 7.10.x to 7.14.3

  1. Download this, and install with the Upgrade Wizard, to upgrade to 7.13:
    Download SuiteCRM-Upgrade-7.10.x-to-7.13.4.zip (SuiteCRM)

  2. Install it with the Upgrade Wizard:
    Go to Admin
    Admin Tools
    Upgrade Wizard
    Follow the instructions on the page.

  3. Download this, and install with the Upgrade Wizard, to get from 7.13 to 7.14.3:
    https://suitecrm.com/download/141/suite714/563702/suitecrm-upgrade-7-13-x-to-7-14-3.zip

  4. Do step 2 (above) to install the upgrade to 7.14.3 (which you downloaded in step 3)…

Reference info here, the Installation Guide, Upgrading: