Probably cuz you're bad
Why Isn't Your Elo Increasing?

You have to understand the gameplay of higher level opponents, i suggest play with a time increment in rapid if u want to gain elo, and carefully study their moves and if possible (and if u are too bad at chess), get a notebook and pen on side and draw all the traps and variation and defense u see... Also learn as many openings as u can
What is your opinion?