If a download gets stuck at 0% or the progress bar freezes, start by canceling the download and trying again. Go to your purchase history, find the app, and tap the cloud icon to reinitiate. If the issue persists, sign out of your Apple ID under Settings → [your name] → Sign Out, then sign back in.
A declined card during purchase usually means the billing address doesn't match what your bank has on file, or the card has expired. Open Settings → [your name] → Payment & Shipping, remove the card, and re-add it with accurate details. If your account has an outstanding balance, Apple blocks new purchases until it's cleared.
If two-factor authentication codes aren't arriving, check that your trusted phone number is still active. You can request the code via a trusted device instead. For repeated login failures, go to iforgot.apple.com to reset credentials — just make sure you're on a stable connection first.
Slow speeds inside the store are rarely the store's fault. Run a quick speed test — if you're below 10 Mbps, the bottleneck is your network. On Wi-Fi, try switching to a different band or moving closer to the router. On cellular, check that App Store isn't restricted under Settings → Cellular → App Store toggle.
Error messages like 'Cannot connect to App Store' typically appear during Apple's maintenance windows or after a system update rollout. Check Apple's System Status page at apple.com/support/systemstatus to see if the storefront is affected. In most cases, waiting 10–15 minutes and retrying is enough.