Issue Description
You have opened your Sections and Elevations to find some or all grid lines are missing.
Solution
Have you checked the layer settings?
Go to Documentation > Layers > Layers (Model View)...
Is the layer on which the grid elements are located set to visible?
Have you checked the Grid Element settings?
Go to Grid Element Settings > Grid Tool.
Ensure that the 'Show Grid Elements' is enabled.
and as a further check select the 'Selected' option for 'Show Grid Elements by Name' and make sure each grid has been selected.
Check the Grid Element settings that the height of the grid elements are correct in relation to your model
TIP: How to place a Grid system.