Anet E10 - Print above 270 °C or "maxtemp" error
Your firmware has set a limit of 270 °C, normally, (default Marlin configured value) this is 275 °C. It appears that the Anet E10 developers have edited the value if you cannot exceed the 270 °C setpoint.
The configuration file for Marlin firmware has the following maximum temperature limit set for the first hotend:
#define HEATER_0_MAXTEMP 275

You can change this yourself, but, you need to flash new firmware, making sure that you're using all the correct settings for this printer model.
As a general remark (for others reading this), you shouldn't simply increase the temperature without changing the hotend (unless it is capable of high temperature printing), if the default hotend is lined with a PTFE tube, the PTFE can form dangerous/toxic gasses at elevated temperatures above 270 °C. But, in your case, an all-metal Micro Swiss hotend is installed that doesn't have the PTFE liner.

Note that the Anet E10 configuration can be found in the Marlin configurations zip file. For the 2.0.7.2 version, the E10 already has the hotend temperature limit increased to 305 °C.