Reasonable is a question even lawyers for the closing are contending with if the closing is delayed for days or even weeks.
What is within reason? In your case, anytime after 1PM is generally acceptable. When your home inspection is cancelled even though it is set within the reasonable time set by the seller once--there should be an extenuating circumstance to deem the cancellation reasonable.
Let us say there was indeed an extenuating circumstance, then this instance can be forgiven.
However, if the sellers cancel again the second inspection which is scheduled during the time that the sellers can accommodate, which is anytime after 1PM, then the sellers reasonable availability is unreasonably unavailable.
Are weekends included on the reasonable availability? If not, then the sellers have the right to refuse to cancel the home inspection. Has there been a miscommunication?
Anyway, as stated earlier by other professionals, there is a home inspection contingency date. If this can't be performed within the set period, just to be on the safe side, have your agent extend the contingency date.
I hope that you can get this done three days before the contingency date to give you some time to get the report especially the water test or any other tests that require laboratory work to get the results.