Colleagues cannot merge two stacks into one (flexstack cisco 2960x)?

Question

Computer networks

Good afternoon, there are two stacks all on 2960x
Switch# Role Mac Address Priority Version State
--------------------------------- ------------------------
*1 Master 0027.9021.a880 15 4 Ready
2 Member 0027.9003.4700 14 4 Ready
3 Member 7486.0baf.4180 13 4 Ready
4 Member 0027.9021.3b00 12 4 Ready
Switch Ports Model SW Version SW Image
------ ----- ----- ---------- -------- --
* 1 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
2 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
3 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
4 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
------------ -------------------------------------------------- ----------------------------------------------------
Switch# Role Mac Address Priority Version State
---------------------------------------------------- -----------
*1 Master 0027.9003.5e80 11 4 Ready
2 Member cc5a.5324.0000 10 4 Ready
Switch Ports Model SW Version SW Image
------ ----- ---- - ---------- ----------
* 1 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
2 52 WS-C2960X-48FPS-L 15.2(4)E3 C2960X-UNIVERSALK9-M
Switch # Port 1 Port 2
-------- ------ ------
1 Down Ok
2 Ok Ok
3 Ok Ok
4 Ok Down
Both stacks are now connected by wires
to down, because they don’t want to be friends with each other, set the required renumber so that there are no problems, delete it from provision, reset it to factory settings, reconnect the stack module, what he didn't do.
I read manuals about Flexstack, you can increase 8 sw, but I don’t get more than 4.
Let me know, thanks in advance.