Can't transfer fuel. How come?

[WolfyDoo]

So I'm doing a challenging moderate KSP playthrough with JNSQ, but how come I can't transfer fuel anymore? Alt clicking won't give the option to transfer fuel from the bottom tank to the upper tank.

https://imgur.com/a/RICfXS2

 

*Already Solved*

Edited July 2, 2022 by WolfyDoo

[Vanamonde]

Glad you were able to figure it out. What did the problem turn out to be? (For the benefit of others who might also have this problem.) 

Meanwhile, this thread has been moved to Gameplay Questions. 

[WolfyDoo]

20 hours ago, Vanamonde said:

Glad you were able to figure it out. What did the problem turn out to be? (For the benefit of others who might also have this problem.) 

Meanwhile, this thread has been moved to Gameplay Questions. 

I had just been very stupid. I have been playing KSP for over 7 years and I just forgot that the R&D in Kerbal Space Center needs to be level 2 for fuel transfers. So leveling up R&D should fix the problem. My apologies for posting the thread in the wrong topic.