@Roberto
Newer plugin may need functions available in osclass 4.x.
You may check intstallation guide:
https://osclass-classifieds.com/installationOsclass upgrade There are just few simple steps to upgrade your osclass to latest version:
- upload osclass ZIP file into your root directory where osclass is installed
- extract ZIP to replace old files
- go to oc-admin, you will be prompted to perform upgrade
- click on "Upgrade now" button
- once finish, everything is updated and ready to use
Make sure to backup your files and database before each upgrade! In case you got stucked on upgrade, restore your database and file system.