Can’t establish a secure connection
This error isn’t browser specific since users haven’t been able to fix it despite changing browsers. The most probable causes for the error are: The first approach upon encountering the error should be checking with others if the application/website is functioning correctly on their system. If not, the server might be down. Otherwise, proceed with the troubleshooting as follows:
1] Download the audio files in the CD to the system first
CD/DVDs were a successful technology when launched. However, they are considered obsolete now. Even though your system might come with a CD/DVD drive, many applications wouldn’t recognize the files. You could download the audio files to your system first and then upload them to Google Play Music.
2] Disable real-time protection of 3rd party anti-virus
It is known that 3rd party anti-virus software products like Avast cause this issue. Many users have confirmed that disabling the anti-virus helped in resolving the problem. However, it isn’t advisable to disable the anti-virus completely. Instead, you could consider disabling real-time protection while uploading the audio files. You can enable the protection later. You could also disable your VPN & Firewall software temporarily and see if it helps.
3] Upload the audio files via the desktop app
While it isn’t a fix, you could use the following workaround to manage the issue in discussion.
Google Play Music provides a desktop app names Music Manager. It could be downloaded from here. Log-in to the Google Play Music app with the same account you used for the browser version and upload the audio/music file to the Music Manager of the app. The files would be uploaded to the server too and you could play them from the browser application directly. Let us know if this helped.