Help looping code inside of a "case"

Using Arduino Programming Questions
7 
char key = keypad.getKey();
  if(key)
  {
    switch(key)
    {

If you don't press a key, the keypad library makes the return value from .getKey() == '\0' and the conditional statementif(key) does not execute.

You can see that with this simple example

void setup() {
  Serial.begin(115200);
  char key = '\0';
  if (key)
    Serial.println("key");
  else
    Serial.println("NoKey");
}

To make the cases repeat with loop() until a new key is pressed try heading your code with this

static char switchKey = '\0';
char key = keypad.getKey();
  if(key != '\0')
    switchKey = key;

  switch(switchKey)
    {
   case '1':

if you want a case to not repeat add switchKey = '\0'; before the break statement in the case.