There is a set of locked candidates, 5 in R1C4 and R1C6 are the only 5s in row 1. One of those two cells must be 5, so no other cell in block 2 can be 5. The puzzle solves with only singles from there.
Hi Jason, Thanks for the forum and the quick response. I've been sudoku-ing in my own little app bubble, so I'm not familiar with the notations you are referencing, i.e. R1C4 and R1C6.
Is there a sticky post explaining that or can you give me a quickie explanation? THANKS!