Hi Mahesh,
Well, I replicated your problem, check below screenshot
Then blank lines are the WBS element area.
Now, you can go to below link in SPRO and see if you the color setting is White
SPRO - SAP NetWeaver - Application Server - Frontend Services - Bar chart - Define fields
To select the correct field, you need to compare the Graphic profile assigned to your PPB profile. As per the information you provided, it is SAPPS_PSST00
In the configuration, check the Form PSST00 and Below as per screenshot
Open this form and check the colour
This should be the combination of your back ground color setup in your user setting for the planning board.
This is just an idea on how the system is behaving, but not sure whether this is the actual issue for your case. Seeing all these setup, it looks like the issue is related to graphic profile or font color setup. Try to change the color and play around, you should be able to fix it.
Also, check for other users, whether they are able to see the text, in such case, check the user settings saved in the planning board assistant. That should fix your issue.
Regards
Terence