Spawning stops after second scene load

I am attempting to create a sort of tower defense game, where there are a certain number of spawns for each enemy type per level...Level 1 = 10 spawns, Level 2 = 12 spawns, etc. I have been using the following code for a button to restart the level.

   // Restart Button
     void Restart()
     {
         // Restart the scene
         SceneManager.LoadScene("Level 1");
         // Resume the normal game speed
         Time.timeScale = 1f;
     }  

This works as intended, so I thought I would use similar functionality to handle going between levels. The idea behind this being that I'm simply increasing the number of spawns/introducing new enemies based on the current level, while maintaining the same scene. With Debug.Log() I have been able to determine that the CurrentLevel value increases between each level, and that the following function actually runs at Start().

 // Function to repeat spawning
 void InvokeSpawn()
 {
     // Invoke the function to repeat based on the Spawn Time
     if (currentLevel <= 5)
     {
         Debug.Log("Enemy1 spawning begun");
         // Spawning Enemy 1
         InvokeRepeating("Spawn_Enemy1", spawnTime, spawnTime);
     }
 }

Unfortunately, the InvokeRepeating function never runs after going to the next level.
Here is the code for spawning the first enemy

         // Enemy 1 Spawn
         void Spawn_Enemy1()
         {
             // Randomly select the next spawn point
             int spawnPointIndex = Random.Range(0, spawnPoints.Length);
     
             // Stop spawning enemies once the counter reaches 0
             if (enemy1Spawns >= 0)
             {
                 Debug.Log("Enemy 1 spawned");
     
                 // Create the enemy at the randomly selected spawn point
                 Instantiate(enemy1, spawnPoints[spawnPointIndex].position, 
  spawnPoints[spawnPointIndex].rotation);
             }
     
             // Decrease the number of spawns
             enemy1Spawns -= 1;
     
             // Decrease total spawns
             totalSpawns -= 1;
         }

And the code when the NextLevel button is clicked

    // Next Level functionality
     public void NextLevel()
     {
         //Reset the score for the current level
         ScoreManager.score = 0;
 
         // Hide the Shop
         shopUI.SetActive(false);
 
         // Increment the current level counter by 1
         GameManager.currentLevel += 1;
 
         // Resume the game
         Time.timeScale = 1f;
 
         // Reload the scene
         SceneManager.LoadScene("Level 1", LoadSceneMode.Single);
     }

I've tried various solutions like ensuring no values are static, different methods of stopping/starting the spawn using InvokeRepeating/CancelInvoke(), and playing with the number of spawns, but nothing has worked. Everything seems to be working correctly and has the appropriate values up until it gets to InvokeRepeating("Spawn_Enemy1") functionality. The only static variables are the CurrentLevel and Score in order to track them between levels. Should that be done differently? Am I missing something here? Perhaps I'm doing something out of order or need to separate some of the functionality? Any help would be great and is always appreciated :)

Edit: I've also attempted starting the game at a higher level (4 for example), which led to the same issue. The appropriate enemies/number of enemies spawned for level 4, but the subsequent level does not spawn anything.