Have you updated to the latest version of PicSender? https://www.picengrave.com/downloads/PicSendersetup.zipHere is the setup Instructions when using Larry's new multimode grbl 1.0c:
Before installing the new version of PicSender, go to the GRBL setup menu and backup your settings for both Spindle & Laser use. Do not name them Spindle.txt or Laser.txt. Exit PicSender.
Install the new version of PicSender and go to the GRBL setup menu. There will be two Modes that you can select. Start with selecting the Spindle Mode if it's not already selected. Click Display Settings and In the left Edit Message window, copy the $30, $31 & $32 grbl settings. Open the file that you backed up previously for Spindle use. Paste the three new grbl settings in after the $27 setting, edit any other settings needed, then Save. By default, the file name will be Spindle.txt. Do not change the file name.
Change to the Laser Mode and click Display Settings again. Repeat copying the three PWM settings, open previously saved Laser backup file and paste those settings in, edit any other settings needed, then Save. By default, the file name will be Laser.txt. Do not change the file name.
When you select the Laser or Spindle Mode in either the GRBL menu or on the main screen, PicSender will send those setting changes to grbl automatically. You can confirm this by selecting the Display Settings button in the GRBL menu, or the GRBL Set button on the main screen after you changed the Mode.