How to increase Top Menu capacity?

I am using the Colinear theme by Automattic. I have apparently reached the maximum number of entries that my main Menu can accommodate. When I try to add another entry I get a “Oops! That page can’t be found” response when I try to update the menu. How can I resolve this so that I can add more entries? Should I just enter Categories (e.g., “Supplements”) in my Menu and change my theme to one that will display all post snippets when a visitor clicks on a category name?

Here’s how my blog looks at the moment: https://naturalremedieshealthyliving.com/