BuildStore works properly in Safari Non-Private browsing mode only. Opening links in Private mode may cause registration loops (when it takes you back to the payment page) and other technical issues. A window that's using Private Browsing has a dark Smart Search field with white text. The white highlight around the word "Private" at the bottom left corner means it is turned on.

Here's a step-by-step guide on how to leave Private mode:

1. Open Safari and tap the icon at the bottom right corner. 
2. Tap Private (lower-left corner) to turn private browsing off, and any Safari windows open in Non-Private Browsing mode will appear. 
3. Tap Done and open builds.io.