Almasi Theme 404 error

I’m having an issue that I have not encountered before. I have been creating a website and in the middle of it, decided to change the theme. I previewed the Alsami theme (the one with the diamond on the preview) and had clicked the customize link (while still in preview. It connected fine that time. I liked the theme and clicked saved and activate. It started the”loading circle spinning in the middle of the page but never loads the activated customize menu page. I clicked the x button and went back to previous page to get to the dashboard menu and tried again and got a 404 error page. I only got it once though. I also refreshed my other browser website viewing tab and the new theme was active. I can access everything else but the customize page. My website is http://www.idl.allstaryouthdrumline.com I hope you can help as I don’t know what else to do. I do not know anything about going into files etc. so if that is needed please tell me how to do it. thanks!!!!!