Flight from Guangzhou or Beijing or Shanghai to Weifang problem

I'm trying to purchase a flight ticket to Weifang either depart from Guangzhou or Beijing or Shanghai between this date 21 to 29 May 2019 but seems to having problem with it. But all flight is available and back to normal from 1st August 2019 onward. Could anyone assist me and let me know what's wrong with the airlines with this flight route ? By the way previously I took Hainan Airlines from Guangzhou to Weifang.

Thanks everyone in advance.