We do not support "downgrading" only upgrading. 

You must wait until your database is upgraded to Odoo 19.0 to switch from Online to VPS hosting.

https://www.odoo.com/documentation/master/administration/supported_versions.html

Hi,

    Your SaaS DB is on 18.2+e, but On Demand only has 18.0, so it’s newer.

    Downgrade is not possible in Odoo.

    Options:

        Wait until On Demand supports 18.2.

        Ask Odoo to move you to Odoo.sh, which matches SaaS versions.

        Use Odoo’s official migration service when the right version is available.

Best step: Open a support ticket with Odoo and request migration when 18.2 is available.

Hope it helps

Migrating your Odoo database requires a compatible version. Directly upgrading from Odoo 18.2 online to a self-hosted Odoo 18 instance isn't directly supported due to database schema differences.

  First, back up your current Odoo 18.2 database. This is crucial to prevent data loss.

  Next, consider using Odoo's official migration tools or a third-party migration service if available. These tools often handle schema updates and data conversions.

  If direct migration isn't feasible, export your data from Odoo 18.2 (using the Odoo export functionality) and then import it into your new Odoo 18 VPS instance. Note that this might require manual data cleaning or adjustments depending on the differences between versions.

Resources:
How to Configure Departments for a Company in Odoo 18 (2025 Guide)
Beyond the Checklist : Modern Odoo CRM Requirements Discovery Strategies for 2025 | Pragmatic Techsoft
Manufacturing Digital Transformation with Odoo | Pragmatic Techsoft
Mastering Seamless Supply Chains | Integrating Odoo 18 with Marketing, Procurement and Logistics
For more complex migrations or assistance, feel free to reach out to Pragmatic Techsoft. We offer Odoo consulting and implementation services.