Error：requiring an unknown u for the problem

General Discussion
1

I have definite the problem and solve, the software said,
image
I don’t know what is wrong.

2

Look at Dirichlet condition
On(… , u= …)
I think you use an other variable
On(…, ???)

3

image
image1219×612 383 KB

you mean the solve (u1) and on (u1)? they match,right?

4

Can you send me the instruction of the line 248

5

After changing the boundary condition，it works. Thanks for your advice.