OctoPrint button doesn't show
Did you find that the green OctoPrint button that is normally found in your printer's control panel has disappeared? There are 2 reasons why the button should not be there anymore. As long as your printer is "Online" or "Not connected" it should be there, but if not, you can try the 2 solutions below.
OctoPrint's interface is limited to the local network on which your Raspberry Pi is set up. This means that you can only access Octoprint from the device you are on when connected to the same Wifi as your Raspberry.
Incorrect IP received
It may happen that your raspberry has not told its IP address to SimplyPrint's server and therefore the button cannot be displayed as there is no link for you to go to. This problem is quickly solved by restarting your raspberry which causes it to resend all information. You can test whether the correct IP is provided to the server by clicking on the gear in the upper right corner of your printer's card in the panel. There you will find "Printer info" and inside you will find a table and a row called "IP address". If you are on the same network as your printer, you can copy the numbers in the field and paste them into the search bar in a new tab. If OctoPrint does not load after that, it is not the correct IP address. If no IP address is displayed in the table, the server has not received an IP at all and your raspberry should be restarted.