Cura 4.3.0 does not pause on Renkforce RF100 V2.2
G-code M0 is not supported!1)
According to the original firmware of the RF100, the firmware is based on Marlin Firmware. From the original sources you can find that in order for M0 (or M1 which is a deprecated alias for M0) to work, you need an ULTRA_LCD supported  LCD panel:

 * "M" Codes
 *
 * M0   - Unconditional stop - Wait for user to press a button on the LCD (Only if ULTRA_LCD is enabled)

However, your printer does not support such an LCD panel, from the configuration.h can be read that the constant is disabled (// means that the line is treated as a comment and as such ignored by the compiler):
//#define ULTRA_LCD  //general LCD support, also 16x2

Therefore, these scripts will not work for your printer!
(Not your printer is running a very old version of Marlin; version 1.0.3)

Solution:
It is possible to manually change the G-code for a (in this case) Marlin based firmware2) (so no adding of a pause by Cura) by inserting a few lines to:

First set relative movement (G91), then retract a certain amount of filament (G1 E-2 F500) or alternatively use G10 using predefined retraction definitions in M207;
Insert a dwell period by inserting the G-code G4 (plus a time to wait), e.g. G4 P2000 to dwell for 2000 milliseconds (alternatively, G4 S2 will also pause for 2 seconds), please adjust the value to an adequate one in which you can insert the object;
First, unretract filament (G1 E2 F500) and then put the printer back in absolute movement (G90 or alternatively use G11 using predefined retraction definitions in M207.


1) By your firmware version/implementation
2) Note that certain G-codes only work for certain firmwares! Fortunately, the original firmware of the RF100 is based on Marlin Firmware (unless it has been changed form the factory default.)