Theme Customizing Stuck and Text font remains Default

I have been using the hueman plugin since 3 years. I have recently installed few plugins for installing instant articles for my blog. However, since last few days, I have noticed that even if I change the color of an anchor text, it still goes back to default which makes the links un-noticable as the text body and the link have same color. Also, when I tried to customize, I cannot because, whenever I click on the “customize” tab of “Apperance ” section on wordpress, it stucks forever without showing anything. Can anyone please help here?