Stop compiling for ESP8266.

I had ESP8266 by ESP8266 Community version 2.5.2 (in Board Manager) installed, was able to compile and load my projects. By some reason I have to decided to temporary downgrade to 2.3.0 and since that I cannot compile my projects even if i have returned back to version 2.5.2. Empty project with two empty functions also not compiles. Projects for Arduino-family (Uno, Mega) are ok. Error message is:
---- 8< ----
Board nodemcuv2 (platform esp8266, package esp8266) is unknown
Error compiling for board NodeMCU 1.0 (ESP-12E Module).
---- 8< ----

My setup: Arduino: 1.8.8 (Windows 8.1), Board: "NodeMCU 1.0 (ESP-12E Module), 80 MHz, Flash, Disabled, All SSL ciphers (most compatible), 4M (no SPIFFS), v2 Lower Memory, Disabled, None, Only Sketch, 115200"

What happened and how to fix??

Something strange is going on :-). I have decided to completely remove ESP8266 support and reinstall it from the scratch. But after removing current (not working) 2.5.2 version by button "Remove" in Boards Manager I have found ESP8266 board is still there, but version has changed to 2.5.1... And now all projects are compiling with no problems :-). Later I have updated 2.5.1 version to latest one, 2.5.2, using "Update" button and now the latest version is also working ok.

Thank you to everybody, problem is fixed! :slight_smile:

Thanks for taking the time to post an update SergeS. I'm glad you got it working. This problem happens on rare occasions when you use the Arduino IDE's Library Manager to update to a new version of a hardware core and a glitch causes it to fail to completely remove the previous version.