I cant build nothing, like in Befwars in LB or in CTF I cant put any block:/

It all started when I uptaded Minecraft, at the beggining I couldnt even enter to Lifeboat server, then I could but when I strated to play I couldnt put any block or build, by now I had only play in CTF and Bedwars and I couldnt build, like I put a block and It just desapeards... but I can hit