How to get Bacteria to attach to an Object?
You're thinking in terms of making them attach to your cloth, but they want to be attached - there are more nutrients and it is safer.  Make sure they have enough light, but not too much, and their nutrients.  They may be attaching and growing, but just not as fast as you expect.
It is also possible that your strain of Cyanobacteria has lost the ability to attach.  If it has been maintained in liquid culture for many generations, any bacteria attached to the wall of the container were selected against.