public class sendAnEmail
{
    

    @InvocableMethod(label='Test' description='sends an email')
       
    public static void sendEmailWithAttachment(List<id> listofQuoteHeader)
    {   
        
     
        Map<Id, Application__c> quotesMap =  new Map<Id, Application__c>([SELECT id,Contact__r.Email,Contact__r.Name FROM Application__c WHERE Id IN :listofQuoteHeader]);
           for(Id QuoteHeaderid :listofQuoteHeader)
           {
               PageReference pref= page.PDFGEN;
               pref.getParameters().put('id',(Id)QuoteHeaderid);
               pref.setRedirect(true);
                system.debug('--appID-'+QuoteHeaderid);
               Attachment attachment = new Attachment();      
               Blob b=pref.getContentAsPDF();
               attachment.Body = b;
               attachment.Name = Datetime.now().format('yyyy-MM-dd HH:mm') + ' ' + 'Quote' + '.pdf';
               attachment.IsPrivate = false;
               attachment.ParentId = QuoteHeaderid;
               attachment.Name='Sign.png';
               insert attachment;
               
               Messaging.SingleEmailMessage semail= new Messaging.SingleEmailMessage();
               Messaging.EmailFileAttachment attach= new Messaging.EmailFileAttachment();
               attach.setFileName('AttachmentEmailFile.pdf');
               attach.setBody(b);
               semail.setSubject('Quote Issued');
            //    String[] emailIds= new String[]{'abc@gmail.com'}; 
            String[] emailIds= new String[]{quotesMap.get(QuoteHeaderid)?.Contact__r.Email};
               semail.setToAddresses(emailIds);
               
               semail.setPlainTextBody('Please find the attached quote details');
               semail.setFileAttachments(new Messaging.EmailFileAttachment[]{attach});
        Messaging.sendEmail(new Messaging.SingleEmailMessage[]{semail});
                  system.debug('----'+listofQuoteHeader);
           } 
        
     SendAnEmail.sendAnEmail();
    }
      
    private static  Application__c account;
     public static void sendAnEmail() {
            system.debug('--check-'+ApexPages.currentPage().getParameters().get('QuoteHeaderid') );
            try{
        account = [SELECT Id, Name  FROM Application__c 
                   WHERE Id = :ApexPages.currentPage().getParameters().get('id')];
               
    }
            catch (Exception e) {
   
    account = new Application__c();
}
        }
        public static Application__c getAccount() {
        return account;
    }

}

I am trying to execute the following code for recalling an approval process an ends up getting the following error

execution of AfterUpdate caused by: System.DmlException: Process failed. First exception on row 0; first error: INVALID_OPERATION, Illegal transition type:

 Approval.ProcessWorkItemRequest pwr = new Approval.ProcessWorkItemRequest();
       
List<ProcessInstance> procins = new List<ProcessInstance>([select Id from ProcessInstance where Status = 'Pending' and TargetObjectId = :objectId]);
// Retrieve the process work instance id associated to the process instance
            List<ProcessInstanceWorkitem>  workitem = new List<ProcessInstanceWorkitem>([select Id from ProcessInstanceWorkitem where ProcessInstanceId = :procins[0].id]);

            if ((workitem != null) && (workitem.size() > 0))
            {
                pwr.SetComments(statusToUpdate);

                pwr.setWorkItemId(workitem[0].id);
                pwr.setAction('Remove');
            
               
                // Execute process request
                Approval.ProcessResult pr = Approval.process(pwr);

}