Have you checked to make sure that you are signed into iTunes on your Mac with the same Apple account that you used when you subscribed to Apple Music?
If so, then here are two articles, both which have troubleshooting steps for you to try:
Access your music collection on all of your devices with Apple Music - Apple Support
If you don't see your entire library after you update iTunes on your Mac or PC - Apple Support
Be aware that there are troubleshooting steps and information regarding limitations for uploading music that was not obtained via Apple Music or the iTunes Store that are embedded in the first article, so it is important to read through all of it carefully. The second one is specifically a troubleshooting article.
Best,
GB