Once you use the Scroll of Ascension it can change your appearance into a Demon or rarely Ferumbras for 5 minutes, or a Fire Effect, and the following message will appear: "Magical sparks whirl around the scroll as you read it and then your appearance is changing." It has a one-hour cooldown. Even if I use it on another character the scroll won't work because it's not tradeable or usable for an hour. This item cannot be used in a swimming pool but can be used in a bathtub, and it doesn't disappear when used.
I tried to use the scroll in a swimming pool, it wouldn't let me and it said "The scroll could get wet, step out of the water first." So I got out of the water but it wouldn't let me use the scroll again until an hour later because it went on cooldown even though it didn't allow me to use it.
I used the scroll while in the bathtub and It actually turned me into a Demon while I was using the Bath Tub. Then I couldn't use the scroll for an hour, nor on another character, but then I was able to use it again after fine no issues.
To sum it up, the scroll has a cooldown of an hour no matter where you use it. I didn't have any issues using it after this. However, what I did notice is that if the item is in my backpack and I'm logged off the cooldown doesn't reset unless I'm online for an hour. If it's in my house the cooldown isn't paused, so it's an hour no matter if you're online or offline. If I'm online or offline and have the item in my depot it's paused unless I'm standing in front of my depot for an hour then the cooldown refreshes. This could be the issue that you were experiencing and why it wouldn't let you use the scroll...
Source- Tibia Fandom