[GNC] Gnucash 3.7 - flatpak cannot recognize second internal HDD & USB Flashdrive

[parag puranik]

My existing system : Mint 19.3 Cinnamon -32 bit with latest updates - (installed on internal SSD) and Gnucash default version 2.6.19. I upgraded Gnucash through Software manager to Build : 3.7+(2019-09-07) -Flatpak. It was successfully installed while keeping my existing default version 2.6.19 intact. My Gnucash working files are stored on attached USB flash drive which I want to open and work upon through Menu>File>open . . . However on doing so my attached (i) second internal HDD and (ii) USB flash drive are not visible at all (even in "+other locations"). Only files in Home folder are visible.  On the other hand, on opening through the earlier ver 2.6.19 these devices are still very well visible. Why this anomaly ? and what is the solution ?