Question: Two separate Flask applications, running on two different subdomains, however the login sessions are not persisting between the subdomains.

For example; logging into a.example.co.uk will result in the user being logged in. However, visiting b.example.co.uk - the user will not be logged in.

Running Apache, Flask (with Flask-Login), Ubuntu 18, Python 3.

App secret is the same on both applications. Tried playing with SERVER\_NAME configuration setting.

Cookies are correctly being set to .example.co.uk

Cookies are configured to be used on any subdomain.

```
SESSION_COOKIE_NAME="example",
SESSION_COOKIE_DOMAIN=".example.co.uk",
REMEMBER_COOKIE_DOMAIN=".example.co.uk",

```

Logging into either subdomain should mean the user is logged into the other.

Answer: 
Managed to solve it! 

Turns out I was setting the Flask application secret keys in the wsgi files, like so;

```
from App import app as application
application.secret_key = 'xxxxxxx'

```

And both the applications had different secret keys in their wsgi files! Completely forgot I was setting the secret keys in both the wsgi file and the main python file.

Removing setting the secret keys from the wsgi files solved my problem
Does it remember when you close out and go back into a.example.co.uk? You need to set REMEMBER\_COOKIE\_SECURE in your config to False or None, can't remember but I had this issue before and that was what solved it. Check out [Flask-Login Documentation](https://flask-login.readthedocs.io/en/latest/#cookie-settings)