Update 2.2.9 changed the way, where you store SRB2 data including addons. Now "/storage/emulated/0/Sonic Robo Blast 2" is default path. Check if "addons" folder is there. If "Sonic Robo Blast 2" directory does not exist, you can run game and quit, which will create it automatically, or create by yourself folder "Sonic Robo Blast 2" with "addons" directory included.