What does the "no pencil" icon mean and why I can't edit sketch?

After importing a DXF as 2D sketch, this icon shows up... a pencil with some blocking icon. I can't edit sketch. Any ideas how to fix it? 

​​​​​​​


For the record it hasn't happened to me before and it's not the first time I'm working with DXF's... although I'm still pretty new to version 2021 been working with 2019 till now.