Arduino Board not detected

[MariaDabukke]

Dear all,
I have a program which use Wemos board before and I have upload it. Afterward, I change the board to Arduino again. After I upload my sketch, the port's not detected. What should I do to fix it?

[DangerToMyself]

Did you have a look at "Port:" under the "Tools" menu? Sometimes, if I disconnect my USB from my computer, when I plug it back in, the program doesn't choose the correct port. May not be your problem. But worth a look.

[MariaDabukke]

Yes, I have check that.

[MariaDabukke]

Eventually, my obsolete Arduino shouldn't be purged. I have install it back, and the port can be detected because I use Arduino 1.8.3 before. But, my obsolete Arduino is version 1.6. It's often being crash, how to fix it?