This plugin hasn’t been supported for the last 6 months according to the plugin’s description.
For the plugin to use version 3 you can change line 133 in ds-sagepay-direct.php
from:
define('VPS_PROTOCOL', 2.23)
to:
define('VPS_PROTOCOL', '3.0');
Don’t forget to include the quotes around the number.
It works fine for me.
NB simulator doesn’t work with version 3. You can only test in ‘Test’ mode
