Parler has had some certificate name issues for a while now. FF may be blocking it, or your malware detection (antivirus) may be blocking it as well.
If so, you should get a warning message and (most) antivirus programs will allow you to ignore the warning and continue to the site.
If you’re not getting any warning and instead, the browser just refuses to connect, delete all the cookies for that domain, restart your browser and attempt to connect again.
DNS issue here. Using OpenDNS for DNS filtering, not Spectrums servers.
Possible, but my professional opinion is DNS.