can 21st mortgage start proceedings

new loan on mobile home. Had a hiccup with paycheck to bank..funds was not there on Aug 1 for the ach pmt. However I contacted my payroll office about why the delay and when full amount of check would be in my bank account-told NLT Aug 18th at the latest. Contacted the mortgage company and let them know...they told me if no pmt made on the 8th..then would start proceedings. This would have been the 3rd pmt on the loan and they using the newness of loan to justify starting proceeding to "repo". Can they do this? On the 18th, current pmt and an extra pmt is scheduled by my bank to send to 21st Mortgage. I have worked for govt 30 years and govt relocated me to Denver.