I have no activated devices listed although Lightroom 6 & Lightroom 3 are both showing as registered along with their serial numbers. LR6 was an upgrade from LR3.
I also lost Photoshop CS5 on my old device but that has activated OK.
When I try to start Lightroom (both license numbers for 6 & 3 were accepted during the install) but I get a message telling me that my serial number is already in use by the maximum allowed computers and I need to deactivate another computer within 30 days.
I get two options only from that screen. Retry activation which just takes me back to the same screen & provide a different serial number which is also useless as I only purchased one Lightroom which is only active on one device currently.
I can't see or find any other options that appear to help.
You need to talk to customer support. They can reset the number of activations for your programs and, in fact, that is the ONLY support they are allowed to provide for CS. When you contact them using either Chat or Phone (see below), tell them you need an ACTIVATION ACCOUNT RESET. Some of the less-trained or newer representative may not be able to help; if so, ask to escalate or ask them to transfer you to a more experienced representative.
Adobe provides support through the Chat function on the contact page or through a phone call. There is no email support.
CHAT: Click the following to contact Adobe customer support staff for help: