Hi, Linda. It doesn't look like your Alexander line, even though you have it entered back to Edward Alexander (1727-1763), connects yet to the rest of the Tree. Since WikiTree considers the genealogy first, and then includes DNA notes on profiles where connections may be possible, you'll have to connect to the main Tree before you'll see any possible matches.
One consideration is that your Alexander line looks to be pretty vertical right now, meaning only parents and one child at each generation. Connections to the larger Tree may be out there and waiting in the form of siblings not yet included in your profiles. If you know of some, I highly recommend you search the Tree for them and, if found, connecting takes only a few mouse-clicks.