Unresolved External using FAnimMontageInstance

Any help would be greatly appreciated.

1>------ Skipped Build: Project: UE4, Configuration: BuiltWithUnrealBuildTool Win32 ------
1>Project not selected to build for this solution configuration
2>------ Build started: Project: CepheusProtocol, Configuration: Development_Editor x64 ------
2>Creating makefile for CepheusProtocolEditor (source directory changed)
2>Using Visual Studio 2017 14.16.27023 toolchain (C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023) and Windows 10.0.17763.0 SDK (C:\Program Files (x86)\Windows Kits\10).
2>Building 3 actions with 8 processes…
2> [1/3] Module.CepheusProtocol.1_of_2.cpp
2> [2/3] UE4Editor-CepheusProtocol.lib
2> Creating library F:\Unreal Projects\CepheusProtocol\Intermediate\Build\Win64\UE4Editor\Development\CepheusProtocol\UE4Editor-CepheusProtocol.lib and object F:\Unreal Projects\CepheusProtocol\Intermediate\Build\Win64\UE4Editor\Development\CepheusProtocol\UE4Editor-CepheusProtocol.exp
2> [3/3] UE4Editor-CepheusProtocol.dll
2> Creating library F:\Unreal Projects\CepheusProtocol\Intermediate\Build\Win64\UE4Editor\Development\CepheusProtocol\UE4Editor-CepheusProtocol.suppressed.lib and object F:\Unreal Projects\CepheusProtocol\Intermediate\Build\Win64\UE4Editor\Development\CepheusProtocol\UE4Editor-CepheusProtocol.suppressed.exp
2>Module.CepheusProtocol.1_of_2.cpp.obj : error LNK2019: unresolved external symbol "public: class FName __cdecl FAnimMontageInstance::GetNextSection(void)const " (?GetNextSection@FAnimMontageInstance@@QEBA?AVFName@@anonymous_user_9674a66c) referenced in function “public: void __cdecl ABase_Character::HandleGrenadeAnimationEnd(void)” (?HandleGrenadeAnimationEnd@ABase_Character@@QEAAXXZ)
2>F:\Unreal Projects\CepheusProtocol\Binaries\Win64\UE4Editor-CepheusProtocol.dll : fatal error LNK1120: 1 unresolved externals
2>UnrealBuildTool : error : UBT ERROR: Failed to produce item: F:\Unreal Projects\CepheusProtocol\Binaries\Win64\UE4Editor-CepheusProtocol.dll
2> (see …/Programs/UnrealBuildTool/Log.txt for full exception trace)
2>Total build time: 26.45 seconds (Parallel executor: 0.00 seconds)
2>C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\Common7\IDE\VC\VCTargets\Microsoft.MakeFile.Targets(44,5): error MSB3075: The command ““C:\Program Files\Epic Games\UE_4.21\Engine\Build\BatchFiles\Build.bat” CepheusProtocolEditor Win64 Development “F:\Unreal Projects\CepheusProtocol\CepheusProtocol.uproject” -WaitMutex -FromMsBuild” exited with code 5. Please verify that you have sufficient rights to run this command.
2>Done building project “CepheusProtocol.vcxproj” – FAILED.
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 1 skipped ==========

FAnimMontageInstance * MontageInstance = GetMesh()->GetAnimInstance()->GetActiveInstanceForMontage(CurrentWeapon->WeaponConfig.GrenadeMontage);

MontageInstance->GetNextSection();