unable to compile sketch

[sparkydave1981]

Unable to compile sketch in Arduino IDE, version 1.8.9

esp8266 board installed in board manager, all libraries as per Git repo installed.

error:
ParadoxAlarmSystemOTA:1:19: error: FS.h: No such file or directory
compilation terminated.
exit status 1
FS.h: No such file or directory

File exists on PC in Arduino library, where is this looking for the file?3

Additional info here:
https://community.home-assistant.io/t/paradox-alarm-panel-wemos-d1-mini-communication/62003/12

[sparkydave1981]

After seeking some help I managed to get the sketch to compile. Settings required:
Arduino IDE version 1.6.13 (wouldn't work with 1.8.9)
ESP8266 core 2.4.1
WifiManager by tzapu 0.12.0
PubSubClient by Nick O`Leary 2.6.0
Arduino JSON lib version 5.13.5 (won't work with version 6.x)

[ghost]

Using Arduino IDE v1.8.12

To add the ESP8266 board to the Boards Manager you will first need to add the URL here:
From "File" -> "Preferences" -> "Additional Boards Manager URLs" add the following text "http://arduino.esp8266.com/stable/package_esp8266com_index.json"

After adding the URL as described above got to "Tools" -> "Board: "some boad" -> "Boards Manager" and install the following:

• "ESP8266 Community" (If the latest version does not work, click on the dropdown button and install v2.6.3)

Install these from "Tools" -> "Manage Libraries":

• WiFiManager by tzapu v0.15.0
• PubSubClient by Nick O'Leary 2.6.0
• Arduino JSON lib version 5.13.5 (does not currently work with version 6.x)

Files to be changed:

• Open webpage.ino:

1. Change "String page = FPSTR(HTTP_HEAD);" to "String page = FPSTR(HTTP_HEADER);"
2. Change "page += FPSTR(HTTP_HEAD_END);" to "page += FPSTR(HTTP_HEADER_END);"

Hope I did not miss anything...