Hi. So I have tried doing a test order before I launch my website using the third party bogus way and just setting my website to test mode so I go to my website in a new tab and try it but both methods said checkout isn't available. Like I would click the button to checkout but it said it wasn't available.
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Congratulations on being close to launching your store. As @hardik355 mentioned in the topics they shared, have you chosen a plan for your store? In order to place a test order, you must select a plan. You won't be charged until your trial expires.
If this is not the issue, can you please confirm if:
From there, if you are still having issues checking out, please share your store URL and I can try running a test order from my end as well.
Also, have you run through our general checklist for starting a new store? It's great to make sure you've checked off all the main items before launching.