I think it's different code with the tutorial that come from here https://developers.chatwoot.com/self-hosted/configuration/multi-factor-authentication:

# Active Record Encryption keys (required for MFA/2FA functionality)
# Replace with the actual keys from rails db:encryption:init output
ACTIVE_RECORD_ENCRYPTION_PRIMARY_KEY=EGY8WhulUOXixybod7ZWwMIL68R9o5kC
ACTIVE_RECORD_ENCRYPTION_DETERMINISTIC_KEY=aPA5XyALhf75NNnMzaspW7akTfZp0lPY
ACTIVE_RECORD_ENCRYPTION_KEY_DERIVATION_SALT=xEY0dt6TZcAMg52K7O84wYzkjvbA62Hz

When I tried your code, now it appears on my dashboard:

# Active Record Encryption keys (required for MFA/2FA functionality)
# Replace with the actual keys from rails db:encryption:init output
export ACTIVE_RECORD_ENCRYPTION_PRIMARY_KEY=string
export ACTIVE_RECORD_ENCRYPTION_DETERMINISTIC_KEY=string
export ACTIVE_RECORD_ENCRYPTION_KEY_DERIVATION_SALT=string

Now, I can see the 2FA option.

Thank you...

1. Go to the web terminal of your Chatwoot application
2. enter rails db:encryption:init
3. Save the strings that is being displayed

active_record_encryption:
  primary_key: string
  deterministic_key: string
  key_derivation_salt: string

4. Go to the file manager of the application
5. Open the env.sh file
6. add these records (replace string with the values from the previous prompt)

# Active Record Encryption keys (required for MFA/2FA functionality)
# Replace with the actual keys from rails db:encryption:init output
export ACTIVE_RECORD_ENCRYPTION_PRIMARY_KEY=string
export ACTIVE_RECORD_ENCRYPTION_DETERMINISTIC_KEY=string
export ACTIVE_RECORD_ENCRYPTION_KEY_DERIVATION_SALT=string

7. restart the app
8. now you can set up 2FA in the user settings.