Hi Vo Nguyen Phuc Ngan,

This looks like a website module configuration issue in Odoo 18 — the restored database has a conflict with the website records. 

What's causing this error?

When you restored the database, Odoo found multiple website records where it expected only one (a "singleton"). This commonly happens when:

• The source and destination databases had different website configurations
• The restore process duplicated website records

How to fix it

1. Go to Settings → activate Developer Mode (add ?debug=1 to URL)
2. Navigate to Website → Configuration → Websites
3. Delete or archive any duplicate website entries, keeping only one

Option 2: Fix via PostgreSQL directly

 sql

-- Connect to your database
psql -d YOUR_DATABASE_NAME

-- Check website records
SELECT id, name, domain, active FROM website;

-- If duplicates exist, deactivate all but the first
UPDATE website SET active = false WHERE id NOT IN (
    SELECT MIN(id) FROM website
);

Open a terminal in your Odoo directory and run:

python odoo-bin shell -d YOUR_DATABASE_NAME 

Then in the shell:

 python

# Check how many website records exist
websites = env['website'].search([])
print(len(websites), websites)

# If there are duplicates, deactivate extras (keep only the first one)
for w in websites[1:]:
    w.write({'active': False})

env.cr.commit()

Restart your Odoo server 

 bash

# Stop the server, then: python odoo-bin -d YOUR_DATABASE_NAME -u website 

Quick question 

When you run the shell command and check len(websites), how many records do you see? That'll confirm whether duplicates are the root cause.

If you have any questions, feel free to reach out.

Hope this helps!

Thanks and Regards,

Email: odoo@aktivsoftware.com

Hi Vo Nguyen Phuc Ngan,

The error you’re seeing:

ValueError: Expected singleton: website()

happens because Odoo is trying to process multiple records where it expects only one. In this case, the website model expects a single website record, but after restoring the database, there might be duplicate website records or an empty record set.

Why it happens after restoring a database:

Restoring the database may have created duplicate entries in website or related models.

Odoo’s website code often uses .ensure_one() to make sure only one record is being processed.

If it finds zero or more than one record, it throws this error.

How to fix it:

Step 1: Check the website records

Activate Developer Mode in Odoo.

Go to Website → Configuration → Websites.

Check if there are multiple websites listed or an empty one.

Step 2: Keep only one active website

Delete duplicates or empty websites.

Make sure exactly one website is active and properly configured.

Step 3: Check website_id in other models

Sometimes models like ir.config_parameter or website.page may reference a deleted or duplicate website.

You can check in Settings → Technical → Database Structure → Models → website if needed.

Step 4: Restart Odoo

After cleaning duplicates, restart the Odoo server.

Refresh the page and open your restored database.

Optional: If you are comfortable with PostgreSQL, you can verify duplicates directly:

SELECT id, name FROM website;

Keep only the correct one

Make a backup before deleting anything!

Hope it will solve your issue.