Go to the layer item details page in Portal for ArcGIS. Is it listed as Feature Layer (hosted)?
What is the data source for the layer in ArcGIS Pro? Is it the service or a database?
From the description you have provided, it sounds like you have registered a feature class in a database as a data store location and published it as a referenced feature service. The service is managed in ArcGIS Server and may not provide editing capabilities. Updates to the source data (in the database) would show in the service.
The alternative is to publish a Hosted Feature Layer. This means the data is copied to the ArcGIS Data Store. It's managed through Portal for ArcGIS. Updates to the original data source in the file/enterprise geodatabase are not shown in the service as it's copied.
If this is not the case, please share as much information as possible, or reach out to your organization's administrator who may be able to help.