Geopackage is not visible in QField offline editing mode

Question

I am using QGIS 3.4.9 Madeira and QField 1.4.4. Having a gpkg and shp layer with the same information in a project and transferring them both to QField (both layers are set to offline editing), only the shapefile layer is visible. The gpkg file is not visible.

• Although gpkg file is not visible, it is editable! When I add a polygon, I see the new polygon in QField with the symbology as set in the QGIS project.
• I have the same issue with a line layer, but not with a point layer
• When using QFieldSync, the plugin asks me always: "do you want to save the changes in the layer Survey_V_Vlakken (offline)"? In other words, it seems that QFieldSync makes a new layer for mobile/offline use?
• Synchronizing back with QField, the changes in the gpkg and shp layers are added to the QGIS project
• First I was using a *.QGZ project (as the default in QGIS 3.4) but I also tried *.QGS and is does not make any difference.
• Both layers have the same CRS 31370 (Belgian Lambert)

Does anyone knows how I can make the gpkg file visible? In a similar question somebody added the same gpkg file as a copy for the QField project; in that way it was visible. But this is not a very handy solution...

Link so similar question

Answer 1

Problem resolved! With a very big thank you @Matthias from OpenGis.ch who was spot on identifying the problem.

I run the Vector > Geometry > Multiple to single algorithm for both layers (polygon and line layer) that didn’t show up. 1/ I found one polygon that was a multi-polygon > when it was fixed, the layer showed up in QField! 2/ Somehow the same problem in the line layer > also fixed! And no longer a question about saving that offline file after running QFieldSync.