Time Machine has stopped working

These instructions worked for me:

To reformat a drive for Time Machine on a Mac, you can use Disk Utility to erase the drive and then set it up in Time Machine: 

1. Open Disk Utility 
2. Select the drive you want to erase 
3. Click Erase 
4. Name the drive 
5. Select the appropriate file system format: 

• • Big Sur and later: Use Apple File System (APFS) 
  • macOS 10.6 (Snow Leopard) to 10.15 (Catalina): Use Mac OS Extended (Journaled), also known as HFS+ 

1. Click Erase again 
2. Open System Preferences 
3. Open Time Machine 
4. Click Select Disk 
5. Select the drive you erased and click Use Disk 

If you're running out of space on your Time Machine backup disk, you can try these options: 

• Delete old backups 
• Use a utility to find large or unnecessary files 
• Choose items to exclude from backups 
• Connect a new, larger backup disk 

So what is the solution?