glue

Hi everyone, I just installed on my T6.1 beach the external water filling pipe union to refil an inside water tank but after few days it come like... unstuck on it's inside part, like it was only glued... It do not looks broken but unglued... how is it possible? Is it made by two different parts...

Alcantara - where are the best places to buy based on price and quality? Best spray adhesive for the above mentioned? Thanks