Some amps/effects seem to be disabled?

Got my QC the other week and super happy with it so far. The only trouble I’ve really had is when building some of my own presets I occasionally find that some amp/effect blocks are greyed out when going to add/change a block. I’m sure there’s a good reason for it but I don’t understand why it’s happening or what I’m doing wrong? Anyone know or experienced it before? Cheers!

You’ve maxed out the CPU for that path. Continue the chain on another row.