using SG 300 switch getting very frequent access port error disabled due to the BPDU

I am doing a lab in GNS for EtherChannel facing issue. below are thinks done with both switches.. 1. port range f1/1 - 32. channel-group 1 mode on3. switchport mode trunk when doing :- show interface trunk its showing status not-trunking. 

I am doing a lab in GNS for EtherChannel facing issue. below are thinks done with both switches.. 1. port range f1/1 - 32. channel-group 1 mode on3. switchport mode trunk when doing :- show interface trunk its showing status not-trunking.