Hi Monica,
When we enable content approval settings in **Library Settings > Versioning settings > Require content approval for submitted items,**when users upload documents to this specific library, the document’s Approval Status is either in:
- Draft (if minor and major versions are enabled) or
- Pending (if only the major version is enabled) state
And there’s no Submit for approval button on the ribbon. The ribbon appears as shown below:

As you have configured approval flows from the Flow menu using Power Automate as described in this
article, I believed this button is attached to the workflow.
Further, as the workflow is configured with flow and to confirm whether this button is linked with the flow or not, , we’ll suggest you post in
Microsoft Power Automate Community for expert assistance. This is a specific channel related to issues with Power Automate/Flow.
The reason we request you to post a new thread is that in
Answers forum, we have limited
resources and very little knowledge about Microsoft Flow/ Power Automate and in
Microsoft Power Automate Community, you will get the most qualified pool of respondents,
and other partners who read the forums regularly can either share their knowledge or learn from your interaction.
Thanks for understanding. Have a nice day and stay safe.
With sincerest regards,
Neha