Si la pantalla no deja de parpadear, no podré iniciar sesión.

Si means if and introduces a condition.

So:

• Si la pantalla no deja de parpadear = If the screen doesn’t stop flickering
• no podré iniciar sesión = I won’t be able to log in

This is a very common pattern in Spanish:

• Si + present tense, future tense
• Example: Si tengo tiempo, te llamo / te llamaré.

In your sentence, the condition is in the present, and the result is in the future.

It can look strange to an English speaker, but it is completely normal in Spanish.

Dejar de + infinitive means to stop + -ing / to stop doing something.

So:

• deja de parpadear = stops flickering
• no deja de parpadear = doesn’t stop flickering / keeps flickering

The no does not cancel anything out. It simply negates the whole expression dejar de parpadear.

Compare:

• La pantalla deja de parpadear. = The screen stops flickering.
• La pantalla no deja de parpadear. = The screen doesn’t stop flickering.

Dejar de + infinitive is a very common structure meaning to stop doing something.

Examples:

• dejar de fumar = to stop smoking
• dejar de hablar = to stop talking
• dejar de funcionar = to stop working
• dejar de parpadear = to stop flickering

So in your sentence, la pantalla no deja de parpadear literally means the screen does not stop flickering.

Yes. Parpadear literally means to blink, especially with your eyes.

But in Spanish it is also used for lights, screens, indicators, and similar things to mean:

• to blink
• to flash
• to flicker

So for a screen, parpadear is very natural.

Examples:

• Me parpadean los ojos. = My eyes are blinking.
• La luz parpadea. = The light is flashing/flickering.
• La pantalla parpadea. = The screen is flickering.

Podré is the future tense of poder: I will be able to.

In the sentence, the speaker is talking about a future result:

• If the screen doesn’t stop flickering, I won’t be able to log in.

That is why podré fits well.

Compare:

• no puedo iniciar sesión = I can’t log in
• no podré iniciar sesión = I won’t be able to log in
• no podría iniciar sesión = I wouldn’t be able to log in

So podré is used because the consequence is seen as something that will happen.

The accent mark shows the stress: po-dré.

This is the future tense form of poder:

• podré
• podrás
• podrá
• podremos
• podréis
• podrán

Many future forms have written accents because the stress falls on the ending.

Also note that poder is irregular in the future:

• not poderé
• but podré

Other similar future irregulars include:

• tendré from tener
• saldré from salir
• haré from hacer

Iniciar sesión means to log in or to sign in.

It is a fixed expression used for websites, apps, devices, and online accounts.

Examples:

• No puedo iniciar sesión. = I can’t log in.
• Tienes que iniciar sesión primero. = You have to log in first.
• He iniciado sesión con mi correo. = I logged in with my email.

In Spain, iniciar sesión is very common in formal or standard digital language. You may also hear:

• entrar en mi cuenta = to get into my account
• acceder = to access

But iniciar sesión is the standard direct equivalent of to log in.

Because Spanish often does not need a subject pronoun when the verb ending already shows who the subject is.

Here, podré already means I will be able.

So Spanish does not need yo unless you want emphasis.

• No podré iniciar sesión. = I won’t be able to log in.
• Yo no podré iniciar sesión. = I won’t be able to log in. / I won’t be able to log in.

The subject yo is understood from the verb form.

In Spanish, articles like el, la, los, las are used more often than in English.

So la pantalla means the screen.

Spanish usually prefers the article when referring to a specific thing already known in the situation, such as the phone screen, laptop screen, or monitor screen being discussed.

Saying just pantalla here would sound incomplete.

The comma separates the if-clause from the main clause:

• Si la pantalla no deja de parpadear,
• no podré iniciar sesión.

This is very common in Spanish writing when the conditional clause comes first.

It helps the sentence read more clearly. In English, you would usually do the same:

• If the screen doesn’t stop flickering, I won’t be able to log in.

Normally, no.

In standard Spanish, after si meaning if, you usually do not use the future tense for real conditions like this.

So the natural structure is:

• Si + present, future
• Si la pantalla no deja de parpadear, no podré iniciar sesión.

Not:

• Si la pantalla no dejará de parpadear... ❌

This is a very important difference from English, because English sometimes allows future meaning after if in ways that can confuse learners. In Spanish, the present tense after si is the normal choice here.

Yes. A few natural alternatives are possible, depending on style:

• Si la pantalla sigue parpadeando, no podré iniciar sesión.
  = If the screen keeps flickering, I won’t be able to log in.

• Si la pantalla no para de parpadear, no podré iniciar sesión.
  = If the screen won’t stop flickering, I won’t be able to log in.

• Si la pantalla continúa parpadeando, no podré iniciar sesión.
  = If the screen continues flickering, I won’t be able to log in.

Your original sentence is perfectly correct and natural. These are just stylistic alternatives.