esp32 use littlefs error

[chuengeric2020]

esp32 uses the file system littlefs in the PageElement SSID_ELM is file:/root.htm
error occurs：
Test complete
[E] [vfs_api.cpp:24] open(): File system is not mounted
[E] [vfs_api.cpp:24] open(): File system is not mounted

code function：
// PB_APPLIED_FILECLASS& FlashFile = PB_APPLIED_FILESYSTEM;
#define FORMAT_LITTLEFS_IF_FAILED true

// Page URIs
#define URI_ROOT "/"
// HTML page declarations.
// root page
PageElement SSID_ELM("file:/connect.htm", {
{ "SSID_LIST", listSSID },
{ "URI_ROOT", [](PageArgument& args) { return URI_ROOT; }}
});
PageBuilder SSID_PAGE(URI_ROOT, { SSID_ELM });
void setup() {
delay(1000);
Serial.begin(115200);
Serial.println();
if(!LittleFS.begin(FORMAT_LITTLEFS_IF_FAILED)){
Serial.println("LittleFS Mount Failed");
return;
}

Serial.println( "Test complete" );

// Prepare HTML page
SSID_PAGE.insert(server);
// Start http server.
// FlashFile.begin();
server.begin();

#please,help to fix bug