spanning-tree issue

I dont know why I'm having this issue but it's happenig. I am working on basic topology. Router to layer 3 switch to little trendnet L2 switch to hosts. Image attached. Very simple. For some reason, the switch in the middle, STP is blocking the port. I have no idea why. How can I fix this and why it this even blocked, there is no redundant links

interface GigabitEthernet0/4
 switchport access vlan 100
 switchport mode access
 switchport nonegotiate
 switchport port-security maximum 4
 switchport port-security violation restrict
 switchport port-security aging time 60
 switchport port-security aging type inactivity
 switchport port-security
 no keepalive
end

TEST_SW#sh spanning-tree blockedports

Name                 Blocked Interfaces List
-------------------- ------------------------------------
VLAN0100             Gi0/4

Number of blocked ports (segments) in the system : 1

There is no even loop. It's one link to the L2 switch thats all.

Can anyone help that actually know whats going on here? Lately I've been getting a lot of answers that were useless to me and did not help. Thank you