Ensure all items are available and unfavorited. Mods have issue with utilizing a favorited tool. Sometimes ensuring tools are in the primary inventory is vital.

I have a similar issue...I have all the items (chain, blowtorch x 2, Welder Mask, Wrench) in my main inventory, and all unfavourited (as per your response above). But the 'Install' button is greyed out?

I also have the necessary skills (Mechanics 4, Metalworking 3). Is there something I am missing? Any help would be greatly appreciated 🤓

In case anyone has this issue, for some reason it seems the upgrades require 1 additional of each material to be in your inventory. Try having extra pipes and metal on hand. Also, chain has several variants. Make sure it's the right one.

i also found out that you need to have enough strength to hold all the materials required in your main inventory (not inside bag), if it's not, the char will just stare blankly and do nothing. i had to drop my bag, all my weapons and anything that is heavy to the ground first in order for me to be able to carry all the materials and start installing the front and side armor. and my strength already maxed too btw.