SII on Rosette shows no detail?

[Rocketman66]

For the first time, I've taken some images using a SII filter of the Rosette Nebula. However, after opening and stretching in PI, there is no nebulosity detail, only stars.
Is this common? Do I need to do anything special with SII to bring out the detail?
Using the same telescope, I took images using Ha and there is plenty of detail.

[chboing]

Hello,
this is what my SII channel on the Rosette looks like, if this can help...
This is clearly the least detailed of the 3, but there are some data still.

[Rocketman66]

Thank you, that's helpful.
I have none of that detail at all. Perhaps a longer exposure is required.

[chboing]

This was 240 seconds with a f/4 telescope 150/600
with a SII filter from zwo, so i think 7nm ? not sure about this