Applying a texture to a mesh created at runtime

I have a mesh object whose vertices and triangles are calculated at runtime. The mesh has a material applied in the inspector which uses this standard URP shader from unity.

When I run the code in editor, the mesh has the correct geometry, but it appears as all one color. As I adjust the texture offset in the material, I see the entire mesh flick to a different color - it's as though only a single point on the texture is being sampled.

I have also tested with a standard plane created from the menu with the same material applied. The texture renders correctly in this case, so the material/shader appears to be doing the right thing.

Here is where I create the mesh (taken from a tutorial I was following but am now starting to deviate from):

 void Awake()
     {
         GetComponent<MeshFilter>().mesh = hexMesh = new Mesh();
         meshCollider = gameObject.AddComponent<MeshCollider>();
         hexMesh.name = "Hex Mesh";
         vertices = new List<Vector3>();
         triangles = new List<int>();
     }
 
     public void Triangulate(HexCell[] cells)
     {
         hexMesh.Clear();
         vertices.Clear();
         triangles.Clear();
         for (int i = 0; i < cells.Length; i++)
         {
             Triangulate(cells[i]);
         }
         hexMesh.vertices = vertices.ToArray();
         hexMesh.triangles = triangles.ToArray();
         hexMesh.RecalculateBounds();
         hexMesh.RecalculateTangents();
         hexMesh.RecalculateNormals();
         meshCollider.sharedMesh = hexMesh;
     }
 
     void Triangulate(HexCell cell)
     {
         Vector3 center = cell.transform.localPosition;
         for(int i =0; i < 6; i++)
         {
             AddTriangle(
             center,
             center + HexMetrics.corners[i],
             center + HexMetrics.corners[i+1]
             );
         }
         
     }
 
     void AddTriangle(Vector3 v1, Vector3 v2, Vector3 v3)
     {
         int vertexIndex = vertices.Count;
         vertices.Add(v1);
         vertices.Add(v2);
         vertices.Add(v3);
         triangles.Add(vertexIndex);
         triangles.Add(vertexIndex + 1);
         triangles.Add(vertexIndex + 2);
     }

Any suggestions on what I am doing wrong?