No limit BUT
The hpv vaccine
is meant to be given three doses over 6-12 months with at least 4 months between dose 1 and 3.
You should try to get the dosing done at the right times, but if you cannot you do not ever need to restart the series, just complete the series as directed once you can. There is no period that is too long in between, but do your best to complete is 6-12 months.