Again, please take the batteries out and have them load tested--only way you will know for sure.
Should have worked on batteries only--the power for the slides is 12 volt. Being plugged in only sends power to the converter that charges the batteries. Clean all terminals on the batteries also.
Let us know what you find.
2015 38RSSA #7382
2005 TK3 #1869, 10 yrs of memories
2017 F450 KR--one more Ford is it
2009 F450 4x4-died; 2010 F450-retired