cannot logon to SAP system after changing parameter

Hi,

I cannot login to SAP system after changing and reverting parameter COMPATIBLE.

History of events:

1. I checked DB16 and the COMPATIBLE parameter was on error:

Value: 10.2.0.3.0 (<> 10.2.0) # Database compatibility mode

2. I tried to change the parameter to the recommended value on SAP note 830576:

ALTER SYSTEM SET COMPATIBLE = '10.2.0' SCOPE=SPFILE;

3. When trying to restart the database I had an error message

so I reverted the parameter to the previous setting with:

ALTER SYSTEM SET COMPATIBLE = '10.2.0.3.0' SCOPE=SPFILE;

4. SAP was started and everything is green:

5. But, when trying to logon, I get an error message when trying to open the logon screen

Please let me know how to solve this.

thanks

Antonio