Customers not showing on customer list.

I can see how you want this resolved so you can work again using the app, Maxower.

Issues like this happen due to a lack of storage space on your phone, corrupted system files, registry errors, or other underlying issues. Since you've already uninstalled and reinstalled the app, and yet the problem persists, I suggest contacting our support team so they can take a look and investigate further. They have the tools to pull up your account in a secure environment and determine what's causing the issue. To do so, follow the steps outlined below:
 

1. Sign in to your QuickBooks Online company.
2. Click Help (?).
3. In the Search bar, select Contact Us to connect with a live support agent.
4. Choose a way to connect with us:
   • Start a chat with a support expert. Live chat all day, M-F.
   • Call us. Mon-Fri, 8:00 AM to 10:00 PM, and Sat-Sun, 8:00 AM to 6:00 PM.

Moreover, check out the available reports that you can use depending on your subscription level. I've added this resource for reference: Reports Included in your QuickBooks Online Subscription. 

Drop your reply below if you have further questions about the customer list on your app. Please know the Community is always here to help you. 

I can confirm the iPhone app is currently 100% broken (nothing is syncing correctly, data / invoices / customers / payments etc are missing). See other forum reports on the issue.

I reported 23rd May. It’s a worldwide issue, with users all reporting slightly different data missing, but the similarity is sync is broken, so data is missing / not synced (totals don’t match etc).

Delete / re-install (and wait for company data to download) is usually the first test / fix for app issues, and at some point it will be the fix…but not until QB have worked out and fixed the sync issue.

After a normal delete / re-install, one of our accounts would take 2-5 minutes to “download company data” (5 years days). Since the bug, it only takes 2 seconds. I’ll know it’s fixed, when it syncs and all the totals match (eg overdue invoices show as 2/3’s what they should be, compared to the web app.

We have multiple accounts and multiple users, so I know when an issue affects everyone…and this affects everyone.

For now, if you want to see correct data on an iPhone, you have to use the web app on Safari via qbo.intuit.com (which is really, really fiddly for the average user to use on an iPhone, so the fix can’t come soon enough).