I can no longer preview, print or export an invoice. I can only email it.

Thanks for bringing this to our attention, Flinthall. Let's refresh your data to ensure you have the latest information available in your QuickBooks app. Allow me to elaborate on this further.

Sometimes, unusual behaviors like this have caused data damage or stored cached files in your QBO iOS app. To help you with the troubleshooting steps, let's reset the app data to refresh your device and set it to its default state. To do these:

1. Navigate to Settings and tap General.
2. Click iPhone Storage, then select the QuickBooks Online app.
3. Then, tap Offload App. This will free up the storage without deleting your app's documents and data.

Once done, re-open the app and log back into your account to check previews on your invoices. I'll include this guide to get the most up-to-date information in QBO: System requirements for QuickBooks Online products.

Alternatively, you can consider utilizing the web browser available on your mobile device. This way, you can efficiently continue managing customer invoices.

Furthermore, I've added this reference to help you track and record customer-paid invoices in your file: Record invoice payments in QuickBooks Online.

Managing customer sales invoices helps maintain a streamlined financial record, Flinthall. Please leave a reply below, and I'll be here whenever you need further assistance with your account. Keep safe.