USCIS announced that they have reached the cap for the first half of FY 2019 already. See their article here.

Any applications received by USCIS for a start date before April 1, 2019 will be now rejected.

There is a congressionally mandated cap of 66,000 and a lottery was used to assign the 33,000 for the first half of the year.

 

USCIS will continue to accept applications for workers who do not fall under the cap. These include:

• Current H-2B workers in the United States petitioning to extend their stay and, if applicable, change the terms of their employment or change their employers;
• Fish roe processors, fish roe technicians, and/or supervisors of fish roe processing; and,
• Workers performing labor or services in the Commonwealth of Northern Mariana Islands and/or Guam from Nov. 28, 2009, until Dec. 21, 2029.