Hi,
You cannot restore 17.4 database to an odoo 18 instance, if you are odoo online wait till it get upgraded into 18 or set up local saas 17.4 instance if you have access to corresponding repositories

Thanks

The issue you're facing is due to the incompatibility between Odoo 17.4 and Odoo 18.0 databases. Restoring a database from a lower version (17.4) into a higher version (18.0) is not supported and can cause errors like the one you're encountering. Additionally, the UnicodeDecodeError suggests that there might be encoding issues with the database or configuration.

Here’s how you can resolve the issue and return to your initial state (Odoo 18.0 with its original database):

Step 1: Stop the Odoo Server

• Ensure that the Odoo server is stopped in PyCharm or via the terminal.

Step 2: Delete the Problematic Database

Since the Database17.4 is causing issues, you need to delete it from PostgreSQL. Follow these steps:

1. Open pgAdmin4 or PostgreSQL CLI:
   • Connect to your PostgreSQL server.
2. Delete the Database:
   • Locate the Database17.4 database in the list of databases.
   • Right-click on it and select Delete/Drop.
   • Confirm the deletion.
   Alternatively, you can use the following SQL command in the PostgreSQL CLI:
   sql
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   DROP DATABASE "Database17.4";

Step 3: Verify the Odoo Configuration File

Ensure that your odoo.conf file is correctly configured to point to your original Odoo 18.0 database. Open the odoo.conf file and check the following parameters:

ini

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[options]
db_host = localhost
db_port = 5432
db_user = odoo
db_password = your_password
db_name = your_original_database_name

Replace your_original_database_name with the name of your original Odoo 18.0 database.

Step 4: Clear Browser Cache

The "Internal Server Error" might be cached in your browser. Clear your browser cache or try accessing Odoo in an incognito/private window.

Step 5: Restart the Odoo Server

• Restart the Odoo server from PyCharm or the terminal.
• Access Odoo via http://localhost:8018.

Step 6: Recreate the Database Manager Link

If you still cannot access the database manager, you can manually recreate the link to the database manager:

1. Open your browser and navigate to:
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   http://localhost:8018/web/database/manager

2. If you see an error, try appending ?debug=1 to the URL to enable debug mode and get more details about the error:
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   http://localhost:8018/web/database/manager?debug=1

Step 7: Recreate the Original Database (If Necessary)

If your original Odoo 18.0 database is corrupted or missing, you can recreate it:

1. Create a New Database:
   • Go to the database manager (http://localhost:8018/web/database/manager).
   • Create a new database with the same name as your original database.
2. Restore a Backup (If Available):
   • If you have a backup of your original Odoo 18.0 database, restore it using the database manager.
3. Reinstall Modules:
   • If you don’t have a backup, you’ll need to reinstall your custom modules and reconfigure your Odoo instance.

Step 8: Prevent Future Issues

• Always ensure that you are restoring a database backup into the same Odoo version or a compatible version.
• Regularly back up your databases to avoid data loss.

Additional Debugging

If the issue persists, check the Odoo logs for more details. The logs can be found in the terminal where you started the Odoo server or in the log file specified in your odoo.conf file (e.g., logfile = /path/to/odoo.log).

By following these steps, you should be able to return to your initial state with Odoo 18.0 and your original database. 

I'm pretty sure the issue is due to the browser cache. Try opening it in a private/incognito window to confirm.  

Thank you Niyas, I am now aware it is not possible. 

The problem is I can't access to my first local odoo 18 database because I did this restore of 17.4 on this instance:

• can't run the instance from pycharm du to the second database "Database17.4" 
• can't access to the database manager from browser because of "internal server error"
• even if I create a new project in pycharm I get the same error due to the database

How can I comme back to my initial state meaning my odoo instance 18.0 + the database 18.0 that was running on it ?

Thank you in advance