Is there an error in your tmp/log/php.log file? Also, check your database for the invoice_items with the greatest value (click on “id” sort once for low to high and then again for high to low). What does this show in the “invoice_id” field? The value in the “id” field contains the invoices table. There has been an issue in the past, where the “invoice_id” gets set to a zero value and so doesn’t show with the invoice., If this is the case, you can manually change the value in the database to fist the unattached invoice item. I would then suggest you perform a clean install of the current version of SI. By clean install, I mean the following:
1) Rename your current SI directory.
2) Download the master_2019.2 SI zip file from github.
3) Unzip the content of the downloaded zip file. Make sure you brows to the root directory for your web applications and then name the folder that will be unzipped to, to the name of your original SI directory renamed in step 1.
4) Copy the config/custom.config.php file from your renamed SI directory (step 1) to the config directory of the newly restored file path.
At this point, you should be able to access your SI app. See if the problem you experienced has been fixed. Note that I assume that you reattached (so to speak) the invoice_items record(s) orphaned in the database to their associated invoices record(s). The verification that this issue has been resolved is that you will see invoice items defined for new and existing invoices properly associated with the invoice.
Let me know how this turns out.