Server.jar cant use more than 2 CPU Cores and when nobody is connected have huge cpu usage

Hello , 14 days ago , i bought a minecraft server at verygames.com a very good server company ! We have a serious problem , every 1.14 snapshot the , server.jar cant use more than 2 cpu cores for the server , leading to massive cpu usage , a 100% usage and the server auto stop for obvious reason of over usage , so we cant play that much , but the 100% not allways appear when we are connected , but ALLWAYS go to 100% in seconds when the server is empty

Thanks