I did find this solution to the problem. I had to search and replace on my website to find all of the old embed codes with user names or user numbers. Then I replaced the first part of the old embed codes up to the playlist numbers and letters with the first part of the new embed code. For my website, I had to use these three basic searches for every user name and number, and I have multiple user names and numbers because the website features playlists from many of the musicians who are part of our world music collaboration. It was a huge effort to accomplish. Spotify should start to respect the work of musicians and artists, and not change codes causing problems for artist's websites unless absolutely necessary due to a security issue or something along those lines, and in such cases, there needs to be a major campaign to let artists and websites know of the coming changes with at least six months of lead time. Content is what is important, not tech for tech sake or shareholder profits.
Here’s the necessary search and replace code. First search your website using these codes after inserting the user name or user number:
<iframe src="https://embed.spotify.com/?uri=spotify%3Auser%3AInsertUserNameHere%3Aplaylist%3A
<iframe src="https://embed.spotify.com/?uri=spotify:user:InsertUserNumberHere:playlist:
<iframe src="https://open.spotify.com/embed/user/InsertUserNumberHere/playlist/
Then replace that part of the code with this:
<iframe style="border-radius:12px" src="https://open.spotify.com/embed/playlist/
Here’s the necessary search and replace code. First search your website using these codes after inserting the user name or user number:
<iframe src="https://embed.spotify.com/?uri=spotify%3Auser%3AInsertUserNameHere%3Aplaylist%3A
<iframe src="https://embed.spotify.com/?uri=spotify:user:InsertUserNumberHere:playlist:
<iframe src="https://open.spotify.com/embed/user/InsertUserNumberHere/playlist/
Then replace that part of the code with this:
<iframe style="border-radius:12px" src="https://open.spotify.com/embed/playlist/