No, you didn't.
Why do you keep using ns=1,s=...?
Just do, what @BRYAN_MOBLEY said: put only [lab_S7_400]DB11,X0.0 in the OpcItemPath.
The syntax DB11,X0.0 is CORRECT one for Ignition.
The DBX0.0 is Siemens syntax in their software (TIA portal, STEP7).
Have you checked DB11 in the PLC (online) that it is configured correctly?
Is address 0.0 in DB (online) really configured as boolean?
Do you REALLY have the latest DB version in the PLC?
Did you configure the PLC as described in the Ignition instructions? Siemens | Ignition User Manual
Also, sometimes it happens, if you repeatedly try to configure a tag with wrong data, that 'something' happens with the Ignition Tag manager (it happened to me a couple of times, especially at the beginning, when I started working with Ignition).
In that case, it is best to delete all tags (first export all tags without the ones you have problems with) and restart Gateway.
Then import the tags back and try to configure the tag again.
Also, show us how did you configured the device connection:
(For s7-300, the CPU slot number is ALWAYS 2.
For s7-400 is 2 or 3, depends of your power supply (if the power supply is narrow one, then it's 2, if it's wide one, then it is 3)).
and how do you have Ignition OPC UA Server configured:
