Howto Fix Retaining Ring on Husqvarna 24C Trimmer?

Recently, the primer bulb cracked and started leaking fuel on my trimmer.

I purchased a new one, but had to ease the red plastic retaining/sealing ring of with the edge of a knife. I could see no other way of doing it and was careful not to break the plastic.

However, when I had replaced the bulb and tried to replace the retaining ring, I couldn't make a solid fix.

I looked inside the ring and it seemed to have what I would describe as some sort of thread, except that it wouldn't thread onto the mounting. There seemed to be no sign of damage.

Should this be secured with some sort of adhesive.