You need to force Electrum to generate addresses until you find the want you want...
In the console tab ("View -> Show console") try the following command:
for x in range(0, 10): print(wallet.create_new_address(False))
That will generate another 10 "receive" addresses... if you don't see the address you need/want, then try:
for x in range(0, 10): print(wallet.create_new_address(True))
That will generate another 10 "change" addresses... if you still don't see the address you need/want, then alternate between the "False" and "True" commands until you find it
(or change the number to 100 to bulk generate addresses!
)