Does your .sdef file in vscode show the airvantage directory:
// Interfaces are searched for in the following directories. Each directory/sub-directory needs to
// be identified here for the system to find and use .api files.
interfaceSearch:
{
// Your project's search paths.
${MY_SYSTEM_DIR}/interfaces
// Legato API search paths.
${LEGATO_ROOT}/interfaces
**${LEGATO_ROOT}/interfaces/airVantage**
${LEGATO_ROOT}/interfaces/atServices
${LEGATO_ROOT}/interfaces/logDaemon
${LEGATO_ROOT}/interfaces/modemServices
${LEGATO_ROOT}/interfaces/portService
${LEGATO_ROOT}/interfaces/positioning
${LEGATO_ROOT}/interfaces/secureStorage
${LEGATO_ROOT}/interfaces/wifi
}
Then you should be giving the path to the .api file in your .cdef file requires api section as below:
// Bind resources from the target module into your application.
requires:
{
// IPC APIs used by this component.
api:
{
airVantage/le_avc.api
}