In many cases the switchport or ESXi pNIC configuration is not correct. Check the switch port configuration (speed: 1000 Mbit, auto-negotiate: enabled). And please check the pNIC settings on your ESXi server that they match the switch port settings.
With the following command you can check the link speed and duplex mode of the pNICs on the ESXi servers:
esxcfg-nics -l
Sometimes the switch port, the SFP module, the cable or the network card of the server is broken, so that only 100 Mbit are negotiated with enabled auto negotiate. You can also try a different cable or switch port as a test.