I can think of a few things

1. What was you viability after digestion? If viability is under 50%, your cells may be too damaged to attach.

2. Have you tried other lots of collagenase?

3. Have you thoroughly removed collagenase before plating? Maybe an additional wash would help.

4. Have you tried alternate substrates like just plain tissue culture plastic or type I collagen? I found that Syrian Golden Hamster fibroblasts attached well to tissue culture plastic or collagen.

Hope this helps!