Did you check fluid level?
I know it’s a bit of a pain, with the reservoir being mounted on the transom, but if fluid is low, it won’t fully extend.
I had that issue with my ‘08 VP SX. The pump does not have a limit switch, you can hear the pump noise change after you hit the limit of ram travel, but the pump keeps going as long as you have your finger in the trim switch. As soon as I topped the fluid, the rams travelled full throw. However, because of the “white plug leak”, I changed the pump cover, that cured the issue…for two years so far.
also, do a search on the issue with that trim system. Specifically, the top of the pump/reservoir, where all the hydraulic lines connect. They were/are notorious for blowing out a small plastic disc, and/or leaking fluid.
the only fix is to purchase a kit, comes with new lines & reservoir cover. I think I laid $475 from a place in New Jersey. It’s an easy job, & you will need two bottles of VP trim oil.
Read Post #4 of this link,that’s the issue with these.
https://forums.iboats.com/threads/problems-with-volvo-penta-sx-a-outdrive.628978/
edited:here’s the HOW TO
https://forums.iboats.com/threads/how-to-volvo-penta-sx-a-dps-trim-pump-replacement.548948/