There is a thread in the forum where "Careeeesa" an Adobe staff member is providing assistance to users of Lightroom version 6 and earlier to install / activate / deactivate. See the link below.
Be, aware Lightroom 6 is no longer supported by Adobe and Apple updated OS do not support these earlier applications, additionally Microsoft is also upgrading their OS.
Win was upgraded to version 11, Apple will be upgraded before the end of October 2021, best you ensure the Auto update feature is not turn on, so you do not get a surprise early one morning. Check before you upgrade your operating system to ensure the applications you depend on will function.
The last update Adobe provided for Lightroom 6 was Dec 2017.