When Lansweeper scans a switch, in most cases it also scans the MAC addresses of all connected devices, per interface. These MAC addresses then get compared with other MAC addresses of assets in your Lansweeper database, when a match is found, this asset is displayed on the switch asset page as connected to the interface in question.
If for some of your switch interfaces only a MAC address is listed in the asset column rather than an assetname, this means this MAC address was not scanned as a part of any device in your database. We expect that in your case the missing access points do not have a MAC address scanned for them. If your access points can be scanned through SNMP, you may still need to enable SNMP on the missing ones. If SNMP cannot be enabled it is likely that a MAC address cannot be retrieved for these devices. Lansweeper can only retrieve the MAC address of devices in the same subnet as your Lansweeper server if no open protocols are available (other than a ping).