Hello Franklin,

probably the two switches build dynamically a trunk link carrying all existing Vlans over the connection or something goes wrong when detecting another switch on the link.

with an IOS based switch the trick could be done by using switchport mode access on both sides.

Be aware that doing this joins two broadcast domains this is usually a fix for some integration but not a good design generally speaking.

if you want to connect the two switches over multiple vlans you should use the switch port template for the port on both sides

So you should use the switch port template (or how it is called in that GUI)

We used a few of these C500 and we found them less friendly then expected

be also aware that they don't support VTP so you need to manually create Vlans on them.

Hope to help

Giuseppe