Due to the limit of chipset and firmware, there is a max number for each powerline network.
TL-PA111, TL-PA4010 v1 – 16 nodes
TL-PA2010 v1, TL-PA211 v1/v2, TL-PA251 v1, TL-WPA271 v1, TL-WPA281, TL-PA411 v1 – 8 nodes
TL-PA210 v1, TL-PA250 v1 – 6 nodes
TL-PA511 v1/v2, TL-PA551 v1 - 64 nodes