Mint LMDE error while installing qTox with Flathub

[kamui69]

Brief Description
OS: Linux Mint LMDE 3 Cindy
qTox version: v1.16.3.
Commit hash: 8eed684
Toxcore-Version: 0.2.3
Qt version: 5.11.3
Hardware: HP usdt 7900, 4GB Core 2 Duo
While installing qTox on Mint Debian Edition I get a error (see below).
qTox is installed, but doesn't work properly.

Reproducible: Always
Steps to reproduce:
Install Qtox with the help of flathub. https://flathub.org/apps/details/io.github.qtox.qTox
Observed Behavior

Error.
While pulling runtime/io.github.qtox.qTox.Locale/x86_64/stable from remote flathub: GPG verification enabled, but no summary signatures found (use gpg-verify-summary=false in remote config to disable)
Expected Behavior

Unable to sent files (attachments) to friends.
Phone connection not yet tested, maybe errors also.