Hi mary1686,
You can try to deactivate all your plugin and try it again. If you cannot live with that, provide me your related url and I will check what can I do for you.
Thanks
I deactivated all my plugin but bold was still not working.
I then re-installed WordPress and the Read theme: at the beginning everything was Ok but as soon as I changed the font from “appareance , customize, fonts” the bold disappeared again.