Having trouble activating abilities during block step

Hi, I've been playing with forge a few months, I got most of it down, but I still run into an issue
that I am unsure how to deal with. I did a for search for the issue first I found no discussions. Creature's with activated mana abilities such as, blight mamba's "pay 1 forest 1 colorless to regenerate". During my declare blockers step, these creature's abilities should be able to activate at instant speed, yet when I click on a creature to activate the ability all I can do is declare the creature a blocker and it is assigned combat damage and I am un-able to use the creature's ability. In some instances I am able to activate abilities before my opponents declare attackers step to circumvent this issue, but I find it quite annoying to deal with, especially with abilities such as regenerate where I would rather use them on reaction to a creature taking combat damage.
I'm not sure if I'm missing something but this is the experience I've run into, not sure if it's a limitation, a bug, or I'm doing something wrong with the interface.
For reference I'm playing on a window's 10 laptop.
Any help with this issue is appreciated, thanks!
that I am unsure how to deal with. I did a for search for the issue first I found no discussions. Creature's with activated mana abilities such as, blight mamba's "pay 1 forest 1 colorless to regenerate". During my declare blockers step, these creature's abilities should be able to activate at instant speed, yet when I click on a creature to activate the ability all I can do is declare the creature a blocker and it is assigned combat damage and I am un-able to use the creature's ability. In some instances I am able to activate abilities before my opponents declare attackers step to circumvent this issue, but I find it quite annoying to deal with, especially with abilities such as regenerate where I would rather use them on reaction to a creature taking combat damage.
I'm not sure if I'm missing something but this is the experience I've run into, not sure if it's a limitation, a bug, or I'm doing something wrong with the interface.
For reference I'm playing on a window's 10 laptop.
Any help with this issue is appreciated, thanks!