Update Assistant shows "Please fix the following error(s)"

The Update Assistant module, formerly called 1-Click Upgrade, checks several requirements before updating. The generic message Please fix the following error(s) (in Spanish back offices, Por favor, corrige el (los) siguiente(s) error(es)) does not identify which one failed.

Keep the requirement shown and the time of the attempt. Then:

1. Check the Update Assistant logs under /directorio-admin/autoupgrade/logs and look for the first failed requirement.
2. Check available space, PHP version, extensions and write access only on the path shown. In current PrestaShop, the theme's asset cache is in /themes/<tema>/assets/cache; /themes/<tema>/cache belongs to old PrestaShop 1.6 themes.
3. If you have SSH, go into modules/autoupgrade and run php bin/console update:check-requirements admin123, replacing admin123 with the actual name of your admin directory. See the official Update Assistant CLI guide.
4. Fix the owner, group or permissions only on the path the check reports as not writable. 755 lets the owner write, but it does not fix an incorrect owner and must not be applied recursively as a universal value.

Make a verified manual backup before updating, even if the module offers its own backup. Repeat the check and confirm that exactly the requirement you fixed disappears before starting the update.

Prepare the update after passing the requirement

Use the version of Update Assistant compatible with the source shop and check the help of the installed command: the options change between versions. The requirements check does not update the shop or replace a full test.

First validate the theme, modules and target version on staging. During the public switchover, keep an eye on orders, cron and payment notifications so that a restore does not discard new transactions. Keep the backup and logs outside the web root and check that the free space also allows for temporary extraction and backup files.