Trying to get Plugins to work in an ABP project but fails to start due to absolute path

I have a project that I want to be able to use plugins with. The project starts and functions as expected without plugins, but when I drop in a plugin I have created it throws an error, call stack:

DEBUG 2020-03-27 15:50:16,144 [1    ] Abp.Modules.AbpModuleManager             - Loading Abp modules...
FATAL 2020-03-27 15:50:16,294 [1    ] Abp.AbpBootstrapper                      - System.ArgumentException: Absolute path information is required. (Parameter 'path')
   at System.Reflection.Assembly.LoadFile(String path)
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Abp.Reflection.AssemblyHelper.GetAllAssembliesInFolder(String folderPath, SearchOption searchOption)
   at Abp.PlugIns.FolderPlugInSource.LoadAssemblies()
   at System.Lazy`1.ViaFactory(LazyThreadSafetyMode mode)
   at System.Lazy`1.ExecutionAndPublication(LazyHelper executionAndPublication, Boolean useDefaultConstructor)
   at System.Lazy`1.CreateValue()
   at Abp.PlugIns.FolderPlugInSource.GetModules()
   at Abp.PlugIns.PlugInSourceExtensions.GetModulesWithAllDependencies(IPlugInSource plugInSource)
   at Abp.PlugIns.PlugInSourceList.<>c.<GetAllModules>b__1_0(IPlugInSource pluginSource)
   at System.Linq.Enumerable.SelectManySingleSelectorIterator`2.MoveNext()
   at System.Linq.Set`1.UnionWith(IEnumerable`1 other)
   at System.Linq.Enumerable.DistinctIterator`1.FillSet()
   at System.Linq.Enumerable.DistinctIterator`1.ToList()
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at Abp.PlugIns.PlugInSourceList.GetAllModules()
   at Abp.Modules.AbpModuleManager.FindAllModuleTypes(List`1& plugInModuleTypes)
   at Abp.Modules.AbpModuleManager.LoadAllModules()
   at Abp.Modules.AbpModuleManager.Initialize(Type startupModule)
   at Abp.AbpBootstrapper.Initialize()

On this line of the Startup file:

app.UseAbp(options => { options.UseAbpRequestLocalization = false; }); // Initializes ABP framework.

The plugin is pretty basic, the only thing I thought it could be I commented out but no luck.

Any tips, help or ideas that would point me in the right direction would be great!

Thank you in advance