When the license key is entered, the message “rekordbox could not write a license file to the following folder. Please check the settings of anti-virus software.” is shown, and activation is not successful.

The security features or software of your OS are preventing the files required for activation from being written to the folder.

If you are using Windows Defender, temporarily disable the [Controlled Folder Access] setting and attempt activation again. (*1)
If you are using security software, temporarily disable [Ransomware protection] and attempt activation again. (*2)

*1 You can also add rekordbox to the list of [Allowed Apps]. For this, use the rekordbox program file (C:\Program Files\Pioneer\rekordbox 5.x.x\rekordbox.exe).

*2 There is also a setting available to set the files to be written to the following folder.

For Mac: /Users/Shared

For Windows: C:\Users\Public\Documents