Without more information, it looks like you have nothing in storage that can be transferred to that hardpoint. Make sure the item you wish to transfer to that hardpoint is actually at the station you're at.
What is it that you're trying to do?
EDIT: It looks more like @GroG79 is right, storage is full...
You can only store 120 modules "in the cloud". How many of those you already have in the "cloud/station storage"?? If you can't dismantle modules it is more than likely you "cloud storage" is full already... Suggestions above do not refer to you ship storage...I want to dismount items, I can't dismount nor weapons nor other items.
This one. The option disappears when your module storage is full. Happened to me just recently. Would be handy if it went red and disabled instead,Sure your storage is not full? 120/120?
Does your ship meet the power requirements? Mass?, if you are at max mass you won't be able to install.
Are you looking to swap a module that won't fit? I thought it redded out as a warning when that happens.