Thanks for confirming the site, @NotRightNow
I believe the issue is that you have all of your items setup for shipping & pickup, however, you do not have your pickup location setup under Fulfillment > Pickup & Delivery. You will need to toggle on the pickup option, or uncheck that as a fulfillment option for your items.
💡 You can quickly bulk edit the fulfillment options by clicking Items > Site Items, then check the boxes for your items. Click on Bulk Edit in the top right corner of the list, then select Fulfillment.
As a test, you can see that this item is the only item on your website that is setup for Delivery (which you happen to have setup instead of Pickup). You also have Delivery as your default setting under Settings > Checkout, and I believe this is what is causing your other items to not show the option to switch to shipping (because they are not marked as having Delivery as a fulfillment method).
To summarize, you can fix your problem by setting up your Pickup location, adding Delivery as a fulfillment option to all items, and/or adjusting your default fulfillment method to your preferred method. Just make sure whatever you set it to, also corresponds with your item, and fulfillment settings.
Please let me know if you have any questions with any of this.
