Got the code working, I forgot to add the sources properly.

Code below for anyone interested

% create the computational grid

Nx = 128; % number of grid points in the x (row) direction

Ny = 128; % number of grid points in the y (column) direction

dx = 0.1e-3; % grid point spacing in the x direction [m]

dy = 0.1e-3; % grid point spacing in the y direction [m]

kgrid = kWaveGrid(Nx, dx, Ny, dy);

% define the properties of the propagation medium

medium.sound_speed = 1500; % [m/s]

medium.alpha_coeff = 0.75; % [dB/(MHz^y cm)]

medium.alpha_power = 1.5;

% create the time array

kgrid.makeTime(medium.sound_speed);

% define a curved transducer element

arc_pos = [20, 20]; % [grid points]

radius = 60; % [grid points]

diameter = 81; % [grid points]

focus_pos = [Nx/2, Nx/2]; % [grid points]

source1.p_mask = makeArc([Nx, Ny], arc_pos, radius, diameter, focus_pos);

% define a time varying sinusoidal source

source_freq = 0.25e6; % [Hz]

source_mag = 0.5; % [Pa]

source1.p = source_mag * sin(2 * pi * source_freq * kgrid.t_array);

% filter the source to remove any high frequencies not supported by the grid

source1.p = filterTimeSeries(kgrid, medium, source1.p);

% create a sensor mask covering the entire computational domain using the

% opposing corners of a rectangle

sensor.mask = [1, 1, Nx, Ny].';

% set the record mode to capture the final wave-field and the statistics at

% each sensor point

%sensor.record = {'p_final', 'p_max', 'p_rms'};

% define a second curved transducer element

arc_pos1 = [20, 108]; % [grid points]

radius1 = 60; % [grid points]

diameter1 = 81; % [grid points]

focus_pos1 = [Nx/2, Nx/2]; % [grid points]

source2.p_mask = makeArc([Nx, Ny], arc_pos1, radius1, diameter1, focus_pos1);

% define a time varying sinusoidal source

source_freq1 = 0.25e6; % [Hz]

source_mag1 = 0.5; % [Pa]

source2.p = source_mag1 * sin(2 * pi * source_freq1 * kgrid.t_array);

% filter the source to remove any high frequencies not supported by the grid

source2.p = filterTimeSeries(kgrid, medium, source2.p);

source.p = source1.p + source2.p;

source.p_mask = source1.p_mask + source2.p_mask;

% create a sensor mask covering the entire computational domain using the

% opposing corners of a rectangle

sensor.mask = [1, 1, Nx, Ny].';

% create a display mask to display the transducer

display_mask = source.p_mask;

% assign the input options

input_args = {'DisplayMask', display_mask, 'PMLInside', false, 'PlotPML', false};

% run the simulation

sensor_data = kspaceFirstOrder2D(kgrid, medium, source, sensor, input_args{:});